PC World Interactive 1

home *** CD-ROM | disk | FTP | other *** search

/ PC World Interactive 1 / PC World Interactive 1 - Nisan 1997.iso / nostalji / bbs / faq / domain.txt < prev next >

Wrap

Internet Message Format | 1995-08-10 | 96.7 KB

From: cdp@njit.edu (Chris Peckham) Subject: comp.protocols.tcp-ip.domains Frequently Asked Questions (FAQ) (Part 1 of 2) Originator: cdp2582@hertz.njit.edu Keywords: BIND,DOMAIN,DNS Sender: news@njit.edu Reply-To: domain-faq@njit.edu (comp.protocols.tcp-ip.domains FAQ comments) Organization: NJIT.EDU - New Jersey Institute of Technology, Newark, NJ, USA Date: Tue, 4 Jul 1995 04:17:24 GMT Approved: news-answers-request@MIT.EDU Expires: Tue 08 Aug 95 00:17:18 EDT Lines: 1338 Posted-By: auto-faq 3.1.1.2 Archive-name: internet/tcp-ip/domains-faq/part1 Revision: 1.6 1995/05/12 18:49:48 This FAQ is edited and maintained by Chris Peckham, <cdp@njit.edu>. The latest version may always be found for anonymous ftp from ftp://rtfm.mit.edu/pub/usenet/news.answers/internet/tcp-ip/domains-faq ftp://ftp.njit.edu/pub/dns/Comp.protocols.tcp-ip.domains.FAQ If you can contribute any answers for items in the TODO section, please do so by sending e-mail to domain-faq@njit.edu ! If you know of any items that are not included and you feel that they should be, send the relevant information to domain-faq@njit.edu. ------------------------------ Date: Fri May 12 14:41:47 EDT 1995 Subject: Table of Contents Table of Contents ================= Part 1 ------ 0. TO DO 1. INTRODUCTION / MISCELLANEOUS 1.1 What is this newsgroup ? 1.2 More information 1.3 What is BIND and where is the latest version of BIND ? 1.4 How can I find the route between systems ? 1.5 Finding the hostname if you have the tcp-ip address 1.6 How to register a domain name 1.7 Change of Domain name 1.8 How memory and CPU does DNS use ? 1.9 Other things to consider when planning your servers 1.10 Proper way to get NS and reverse IP records into DNS 1.11 How to get my address assign from NIC? 1.12 Is there a block of private IP addresses I can use? 1.13 Cache failed lookups 1.14 What does an NS record really do ? 1.15 DNS ports 1.16 Obtaining the latest cache file 2. UTILITIES 2.1 Utilities to administer DNS zone files 2.2 DIG - Domain Internet Groper 2.3 DNS packet analyzer 2.4 host 2.5 Programming with DNS 2.6 A source of information relating to DNS 3. DEFINITIONS 3.1 TCP/IP Host Naming Conventions 3.2 Slaves and servers with forwarders 3.3 When is a server authoritative? 3.4 Underscore in host-/domain names 3.5 Lame delegation 3.6 What does opt-class field do? 3.7 Top level domains 3.8 Classes of networks 3.9 What is CIDR ? 3.10 What is the rule for glue ? Part 2 ------ 4. CONFIGURATION 4.1 Changing a Secondary server to a Primary 4.2 How do I subnet a Class B Address ? 4.3 Subnetted domain name service 4.4 Recommended format/style of DNS files 4.5 DNS on a system not connected to the Internet 4.6 Multiple Domain configuration 4.7 wildcard MX records 4.8 How to identify a wildcard MX record 4.9 Why are fully qualified domain names recommended ? 4.10 Distributing load using named 4.11 Order of returned records 4.12 resolv.conf 4.13 Delegating authority 4.14 DNS instead of NIS on a Sun OS 4.1.x system 5. PROBLEMS 5.1 No address for root server 5.2 Error - No Root Nameservers for Class XX 5.3 Bind 4.9.x and MX querying? 5.4 Some root nameservers don't know localhost 5.5 MX records and CNAMES and separate A records for MX targets 5.6 NS is a CNAME 5.7 Nameserver forgets own A record 5.8 General problems (core dumps !) 5.9 malloc and DECstations 6. ACKNOWLEDGEMENTS ------------------------------ Date: Wed May 3 12:55:13 EDT 1995 Subject: Q0 - TO DO list * How to do an initial installation * How to change service providers (what happens) * Explain the difference between BIND (an implementation) and DNS (spec) * Expand the slave/forward section of Q 3.2 * Add a definition of a "private domain" in discussion (or cut it out) * mention mail-to-news gateways for newsgroup, mailing lists, anonymous ftp, etc in what is newsgroup section * The evils of wildcard MX records ------------------------------- Date: Thu Dec 1 11:08:28 EST 1994 Subject: Q1.1 - What is this newsgroup ? comp.protocols.tcp-ip.domains is the usenet newsgroup for discussion on issues relating to the Domain Name System (DNS). This newsgroup is not for issues directly relating to IP routing and addressing. Issues of that nature should be directed towards comp.protocols.tcp-ip. ------------------------------- Date: Fri May 12 13:54:01 EDT 1995 Subject: Q1.2 - More information You can find more information concerning DNS in the following places: * The BOG (BIND Operations Guide) - in the BIND distribution * The FAQ included with bind4.9.3 doc/misc/FAQ * DNS and BIND by Albitz and Liu (an O'Reilly & Associates Nutshell handbook) * A number of RFCs (920, 974, 1032, 1034, 1101, 1123, 1178, 1183, 1348, 1535, 1536, 1537, 1591, 1706, 1712, 1713) * The DNS Resource Directory (DNSRD) http://www.dns.net/dnsrd * If you are having troubles relating to sendmail and DNS, you may wish to refer to the USEnet newsgroup comp.mail.sendmail and/or the FAQ for that newsgroup ftp://rtfm.mit.edu/pub/usenet/news.answers/mail/sendmail-faq * Information concerning some frequently asked questions relating to the Internet (i.e., what is the InterNIC, what is an RFC, what is the IETF, etc) may be found for anonymous ftp from ftp://ds.internic.net/fyi/fyi4.txt A version may also be obtained with the URL gopher://ds.internic.net/00/fyi/fyi4.txt ------------------------------- Date: Fri Apr 28 13:42:09 EDT 1995 Subject: Q1.3 - What is BIND and where is the latest version of BIND ? Q: What is BIND ? A: From the BOG Introduction - The Berkeley Internet Name Domain (BIND) implements an Internet name server for the BSD operating system. The BIND consists of a server (or ``daemon'') and a resolver library. A name server is a network service that enables clients to name resources or objects and share this information with other objects in the network. This in effect is a distributed data base system for objects in a computer network. BIND is fully integrated into BSD (4.3 and later releases) network programs for use in storing and retrieving host names and address. The system administrator can configure the system to use BIND as a replacement to the older host table lookup of information in the network hosts file /etc/hosts. The default configuration for BSD uses BIND. Q: Where is the latest non-beta version of BIND ? A: The latest non-beta version of BIND is version 4.9.2. This can be found for anonymous ftp from ftp://gatekeeper.dec.com/pub/misc/vixie/4.9.2-940221.tar.gz Q: Where is the latest version of 4.9.3 located ? A: You can reference this URL: http://www.isc.org/isc/ At this time, the latest version of 4.9.3 may be found for anonymous ftp from ftp://ftp.vix.com/pri/vixie/bind-4.9.3-BETA17.tar.gz Size: 1532332 bytes BSD checksum: 36044 1497 POSIX checksum: 3451112785 1532332 MD5 checksum: 604340af2eb7225819264c2ccf592bbd You won't be able to "ls" or "dir" the file. You must "cd" (inside of FTP) to the remote directory (/pri/vixie) unless you plan to create a local /pri/vixie or unless you plan to give "get" a second argument. You can't ping this ftp server, ever. To retrieve this file, do this: $ ftp ftp.vix.com user: anonymous password: (your e-mail address) ftp> cd /pri/vixie ftp> binary ftp> get bind-4.9.3-BETA17.tar.gz ftp> quit You will need GNU zip, Larry Wall's patch program (if there are any patch files), and a C compiler to get BIND running from the above mentioned source. GNU zip is available for anonymous ftp from ftp://prep.ai.mit.edu/pub/gnu/gzip-1.2.4.tar patch is available for anonymous ftp from ftp://prep.ai.mit.edu/pub/gnu/patch-2.1.tar.gz ------------------------------ Date: Mon Jan 2 13:27:27 EST 1995 Subject: Q1.4 - How can I find the route between systems Q: How can I find the path taken by packets between two systems/domains ? A: Get the source of the 'traceroute' command, compile it and install it on your system. One version of this program with additional functionality may be found for anonymous ftp from ftp://ftp.nikhef.nl/pub/network/traceroute.tar.Z This package is mirrored at ftp://ftp.njit.edu/pub/dns/nikhef/traceroute.tar.Z Another version may be found for anonymous ftp from ftp://ftp.psc.edu/pub/net_tools/traceroute.tar ------------------------------ Date: Thu Dec 1 09:55:24 EST 1994 Subject: Q1.5 - Finding the hostname if you have the tcp-ip address Q: Can someone tell me how can I find the name of the domain if I know the tcp-ip address of the domain? Is there some kind of service for this? A: For an address a.b.c.d you can always do: % nslookup > set q=ptr > d.c.b.a.in-addr.arpa. Most newer version of nslookup (since 4.8.3) will recognize an address, so you can just say: % nslookup a.b.c.d DiG will work like this also: $ dig -x a.b.c.d Host from the contrib/host from the bind distribution may also be used. ------------------------------- Date: Fri Apr 28 13:16:32 EDT 1995 Subject: Q1.6 - How to register a domain name Q: I would like to register a domain. How do I do this ? Can a name be reserved, or must we already have an IP address and be hooked up to the Internet before obtaining a domain name? A: You can talk to your Internet Service Provider (ISP). They can submit the registration for you. If you are not going to be directly connected, they should be able to offer MX records for your domain for mail delivery (so that mail sent to the new domain will be sent to your "standard" account). In the case where the registration is done by the organization itself, it still makes the whole process much easier if the ISP is approached for secondary servers _before_ the InterNIC is approached for registration. For information about making the registration yourself, look to the InterNIC ! ftp://internic.net/templates/ gopher://rs.internic.net/ http://www.internic.net/infoguide.html http://www.ripe.net You will need at least two domain name servers when you register your domain. Many ISP's are willing to provide primary and/or secondary name service for their customers. Many times, registration of a domain name can be initiated by sending e-mail to the zone contact. You can obtain the contact in the SOA record for the country, or in a whois server: $ nslookup -type=SOA fr. origin = ns1.nic.fr mail addr = nic.nic.fr ... The mail address to contact in this case is 'nic@nic.fr' (you must substitute an '@' for the first dot in the mail addr field). An alternate method to obtain the e-mail address of the national NIC is the 'whois' server at InterNIC. You may be requested to make your request to another email address or using a certain information template/application. ------------------------------- Date: Sun Nov 27 23:32:41 EST 1994 Subject: Q1.7 - Change of Domain name Q: We are preparing for a change of our domain name: abc.foobar.com -> foobar.net What are the tricks and caveats we should be aware of ? A: The forward zones are easy and there are a number of ways to do it. One way is the following: Have a single db file for the 2 domains, and have a single machine be the primary server for both abc.foobar.com and foobar.net. To resolve the host foo in both domains, use a single zone file which merely uses this for the host: foo IN A 1.2.3.4 Use a "@" wherever the domain would be used ie for the SOA: @ IN SOA (... Then use this pair of lines in your named.boot: primary abc.foobar.com db.foobar primary foobar.net db.foobar The reverse zones should either contain PTRs to both names, or to whichever name you believe to be canonical currently. ------------------------------- Date: Fri Apr 28 13:52:20 EDT 1995 Subject: Q1.8 - How memory and CPU does DNS use ? Q: How much memory and CPU does DNS use ? A: It can use quite a bit ! The main thing that BIND needs is memory. It uses very little CPU or network bandwidth. The main considerations to keep in mind when planning are: 1) How many zones do you have and how large are they ? 2) How many clients do you expect to serve and how active are they ? As an example, here is a snapshot of memory usage from CSIRO Division of Mathematics and Statistics, Australia Named takes several days to stabalize its memory usage. Our main server stabalises at ~10Mb. It takes about 3 days to reach this size from 6 M at startup. This is under Sun OS 4.1.3U1. As another example, here is the configuration of ns.uu.net (from late 1994): ns.uu.net only does nameservice. It is running a version of BIND 4.9.3 on a Sun Classic with 96 MB of RAM, 220 MB of swap (remember that Sun OS will reserve swap for each fork, even if it is not needed) running Sun OS 4.1.3_U1. Joseph Malcolm, of Alternet, states that named generally hovers at 5-10% of the CPU, except after a reload, when it eats it all. He also states that if you are interested in the network connectivity around the system (ns.uu.net is located off of Falls-Church4), a PostScript map is available for anonymous ftp from ftp://ftp.uu.net/uunet-info/alternet.map.ps ------------------------------- Date: Mon Jan 2 14:24:51 EST 1995 Subject: Q1.9 - Other things to consider when planning your servers When making the plans to set up your servers, you may want to also consider the following issues: A) Server O/S limitations/capacities (which tend to be widely divergent from vendor to vendor) B) Client resolver behavior (even more widely divergent) C) Expected query response time D) Redundancy E) Desired speed of change propagation F) Network bandwidth availability G) Number of zones/subdomain-levels desired H) Richness of data stored (redundant MX records? HINFO records?) I) Ease of administration desired J) Network topology (impacts reverse-zone volume) Assuming a best-possible case for the factors above, particularly (A), (B), (C), (F), (G) & (H), it would be possible to run a 1000-node domain using a single lowly 25 or 40 MHz 386 PC with a fairly modest amount of RAM by today's standards, e.g. 4 or 8 Meg. However, this configuration would be slow, unreliable, and would provide no functionality beyond your basic address-to-name and name-to-address mappings. Beyond that baseline case, depending on what factors listed above, you may want look at other strategies, such splitting up the DNS traffic among several machines strategically located, possibly larger ones, and/or subdividing your domain itself. There are many options, tradeoffs, and DNS architectural paradigms from which to choose. ------------------------------ Date: Mon Jan 2 13:03:53 EST 1995 Subject: Q1.10 - Proper way to get NS and reverse IP records into DNS Q: Reverse domain registration is separate from forward domain registration. How do I get it updated ? A: Blocks of network addresses have been delegated by the InterNIC. Check if your network a.b.c.0 is in such a block by using nslookup: nslookup -type=soa c.b.a.in-addr.arpa. nslookup -type=soa b.a.in-addr.arpa. nslookup -type=soa a.in-addr.arpa. One of the above should give you the information you are looking for (the others will return with an error something like `*** No start of authority (SOA) records available for ...') This will give you the email address of the person to whom you should address your change request. If none of these works, your network probably has not been delegated by the InterNIC and you need to contact them directly. CIDR has meant that the registration is delegated, but registration of in-addr.arpa has always been separate from forward zones - and for good reason - in that the forward and reverse zones may have different policies, contents etc, may be served by a different set of nameservers, and exist at different times (usually only at point of creation). There isn't a one-to-one mapping between the two, so merging the registration would probably cause more problems than people forgetting/not-knowing that they had to register in-addr.arpa zones separately. For example, there are organizations that have hundreds of networks and two or more domains, with a sprinkling of machines from each network in each of the domains. ------------------------------- Date: Mon Jan 2 13:08:38 EST 1995 Subject: Q1.11 - How to get my address assign from NIC ? Q: Can anyone tell me how can I get the address from NIC? How many subnets will NIC give to me? A: You should probably ask your Internet provider to give you an address. These days, addresses are being distributed through the providers, so that they can assign adjacent blocks of addresses to sites that go through the same provider, to permit more efficient routing on the backbones. Unless you have thousands of hosts, you probably won't be able to get a class B these days. Instead, you can get a series of class C networks. Large requests will be queried, so be ready to provide a network plan if you ask for more than 16 class C networks. If you can't do this through your Internet provider, you can look for a subnet registration form on rs.internic.net. See the answer in this FAQ to the question "How to register a domain name" for a URL to these forms. ------------------------------- Date: Mon Jan 2 13:12:01 EST 1995 Subject: Q1.12 -Is there a block of private IP addresses I can use? Q: Is there a block of private IP addresses I can use? A: This answer may be found in the FAQ for the newsgroup comp.dcom.sys.cisco available for anonymous ftp from ftp://rtfm.mit.edu/pub/usenet/comp.dcom.sys.cisco There is a block of private IP addresses that you can use. However whether you wish to do so is an issue of some debate. There are two RFCs which discuss this issue, and present opposing views: 1597 Address Allocation for Private Internets. Y. Rekhter, B. Moskowitz, D. Karrenberg & G. de Groot. March 1994. (Format: TXT=17430 bytes) 1627 Network 10 Considered Harmful (Some Practices Shouldn't be Codified). E. Lear, E. Fair, D. Crocker & T. Kessler. June 1994. (Format: TXT=18823 bytes) Neither one of these RFCs is anything more than a set of informational guidelines; they are *not* words to live by (remember that RFC stands for Request For Comments). If you're seriously considering using private IP addresses, please read them both. In any event, RFC 1597 documents the allocation of the following addresses for use by ``private internets'': 10.0.0.0 - 10.255.255.255 172.16.0.0 - 172.31.255.255 192.168.0.0 - 192.168.255.255 Most importantly, it is vital that nothing using these addresses should ever connect to the global Internet, or have plans to do so. Please read the above RFCs before considering implementing such a policy. ------------------------------- Date: Mon Jan 2 13:55:50 EST 1995 Subject: Q1.13 - Cache failed lookups Q: Does BIND cache negative answers (failed DNS lookups) ? A: Yes, BIND 4.9.3 will cache negative answers. ------------------------------- Date: Fri Feb 10 15:35:07 EST 1995 Subject: Q1.14 - What does an NS record really do ? Q: What does a NS record really do ? A: The NS records in your zone data file pointing to the zone's name servers (as opposed to the servers of delegated subdomains) don't do much. They're essentially unused, though they are returned in the authority section of reply packets from your name servers. ------------------------------- Date: Fri Feb 10 15:40:10 EST 1995 Subject: Q1.15 - DNS ports Q: Does anyone out there have any information/experience on exactly which TCP/UDP ports DNS uses to send and receive queries ? A: Use the following chart: Prot Src Dst Use udp 53 53 Queries between servers (eg, recursive queries) Replies to above tcp 53 53 Queries with long replies between servers, zone transfers Replies to above udp >1023 53 Client queries (sendmail, nslookup, etc ...) udp 53 >1023 Replies to above tcp >1023 53 Client queries with long replies tcp 53 >1023 Replies to above Note: >1023 is for non-priv ports on Un*x clients. On other client types, the limit may be more or less. Another point to keep in mind when designing filters for DNS is that a DNS server uses port 53 both as the source and destination for it's queries. So, a client queries an initial server from an unreserved port number to UDP port 53. If the server needs to query another server to get the required info, it sends a UDP query to that server with both source and destination ports set to 53. The response is then sent with the same src=53 dest=53 to the first server which then responds to the original client from port 53 to the original source port number. The point of all this is that putting in filters to only allow UDP between a high port and port 53 will not work correctly, you must also allow the port 53 to port 53 UDP to get through. Also, ALL versions of BIND use TCP for queries in some cases. The original query is tried using UDP. If the response is longer than the allocated buffer, the resolver will retry the query using a TCP connection. If you block access to TCP port 53 as suggested above, you may find that some things don't work. Newer version of BIND allow you to configure a list of IP addresses from which to allow zone transfers. This mechanism can be used to prevent people from outside downloading your entire namespace. ------------------------------- Date: Fri Apr 28 14:19:10 EDT 1995 Subject: Q1.16 - Obtaining the latest cache file Q: What is the cache file and where can I obtain the latest version ? A: From the "Name Server Operations Guide" 6.3. Cache Initialization 6.3.1. root.cache The name server needs to know the servers that are the authoritative name servers for the root domain of the network. To do this we have to prime the name server's cache with the addresses of these higher authorities. The location of this file is specified in the boot file. ... A copy of the comments in the file available from the InterNIC follow: ; This file holds the information on root name servers needed to ; initialize cache of Internet domain name servers ; (e.g. reference this file in the "cache . <file>" ; configuration file of BIND domain name servers). ; ; This file is made available by InterNIC registration services ; under anonymous FTP as ; file /domain/named.root ; on server FTP.RS.INTERNIC.NET ; -OR- under Gopher at RS.INTERNIC.NET ; under menu InterNIC Registration Services (NSI) ; submenu InterNIC Registration Archives ; file named.root ; ; last update: Oct 5, 1994 ; related version of root zone: 1994100500 ; If you have a version of dig running, you may obtain the information with the command dig @ns.internic.net . ns ------------------------------- Date: Mon Jan 2 13:13:49 EST 1995 Subject: Q2.1 - Utilities to administer DNS zone files Q: I am wondering if there are utilities available to ease the administration of the zone files in the DNS. A: There are a few. Two common ones are h2n and makezones. Both are perl scripts. h2n is used to convert host tables into zone data files. It is available for anonymous ftp from ftp://ftp.uu.net/published/oreilly/nutshell/dnsbind/dns.tar.Z. makezones works from a single file that looks like a forward zone file, with some additional syntax for special cases. It is included in the current BIND distribution. The newest version is always available for anonymous ftp from ftp://ftp.cus.cam.ac.uk/pub/software/programs/DNS/makezones This package is mirrored at ftp://ftp.njit.edu/pub/dns/cus.cam.ac/makezones More information may be found using the DNS Resource Directory http://www.dns.net/dnsrd ------------------------------- Date: Thu Dec 1 11:09:11 EST 1994 Subject: Q2.2 - DIG - Domain Internet Groper Q: Where can I find the latest version of DIG ? A: The latest and greatest, official, accept-no-substitutes version of DiG is the one that comes with BIND. Get the latest kit. ------------------------------- Date: Mon May 15 12:57:42 EDT 1995 Subject: Q2.3 -DNS packet analyser Q: I'm looking for a Ethernet packet analyser of public domain or standard (like tcpdump, snoop, packetman) that is able to determine DNS data field protocol A: There is a free ethernet analyser called Ethload available for PC's running DOS. The latest filename is ETHLD104.ZIP. It understands lots of protocols including TCP/UDP. It'll look inside there and display DNS/BOOTP/ICMP packets etc. (Ed. note: something nice for someone to add to tcpdump ;^) ). Depending on the ethernet controller it's given it'll perform slightly differently. It handles NDIS/Novell/Packet drivers. It works best with Novell's promiscuous mode drivers. A A SimTel mirror site should have the program available for anonymous ftp. As an example, ftp://oak.oakland.edu/SimTel/msdos/lan/ethld104.zip ------------------------------- Date: Sun Dec 4 21:15:38 EST 1994 Subject: Q2.4 - host A section from the host man page: host looks for information about Internet hosts and domain names. It gets this information from a set of intercon- nected servers that are spread across the world. The infor- mation is stored in the form of "resource records" belonging to hierarchically organized "zones". By default, the program simply converts between host names and Internet addresses. However, with the -t, -a and -v options, it can be used to find all of the information about domain names that is maintained by the domain nameserver system. The information printed consists of various fields of the associated resource records that were retrieved. The arguments can be either host names (domain names) or numeric Internet addresses. 'host' is compatible with both BIND 4.9 and BIND 4.8 'host' may be found in contrib/host in the BIND distribution. The latest version always available for anonymous ftp from ftp://ftp.nikhef.nl/pub/network/host.tar.Z It may also be found for anonymous ftp from ftp://ftp.uu.net/networking/ip/dns/host.tar.Z ------------------------------- Date: Fri Feb 10 15:25:11 EST 1995 Subject: Q2.5 - Programming with DNS Q: How can I use DNS information in my program? A: It depends on precisely what you want to do: a) Consider whether you need to write a program at all. It may well be easier to write a shell program (e.g. using awk or perl) to parse the output of dig, host or nslookup. b) If all you need is names and addresses, there will probably be system routines 'gethostbyname' and 'gethostbyaddr' to provide this information. c) If you need more details, then there are system routines (res_query and res_search) to assist with making and sending DNS queries. However, these do not include a routine to parse the resulting answer (although routines to assist in this task are provided). There is a separate library available that will take a DNS response and unpick it into its constituent parts, returning a C structure that can be used by the program. The source for this library is available for anonymous ftp from ftp://hpux.csc.liv.ac.uk/hpux/Networking/Admin/resparse-* ------------------------------- Date: Wed May 3 12:46:50 EDT 1995 Subject: Q2.6 - A source of information relating to DNS Q: Where can I find utilities and tools to help me manage my zone files ? A: There are several tools available. Please refer to the "tools" section of the DNS resources directory: http://www.dns.net/dnsrd/tools.html ------------------------------- Date: Fri May 12 14:33:40 EDT 1995 Subject: Q3.1 - TCP/IP Host Naming Conventions Q: Is a guide available relating to naming systems ? A: One guide/resource is RFC 1178, "Choosing a Name for Your Computer", which is available via anonymous FTP from ftp://ftp.internic.netrfc/rfc1178.txt RFCs (Request For Comments) are specifications and guidelines for how many aspects of TCP/IP and the Internet (should) work. Most RFCs are fairly technical documents, and some have semantics that are hotly contested in the newsgroups. But a few, like RFC 1178, are actually good to read for someone who's just starting along a TCP/IP path. ------------------------------- Date: Thu Dec 1 10:32:43 EST 1994 Subject: Q3.2 - What are slaves and forwarders ? Q: What are slaves and forwarders ? A: "forwarders" is a list of NS records that are _prepended_ to a list of NS records to query if the data is not available locally. This allows a rich cache of records to be built up at a centralized location. This is good for sites that have sporadic or very slow connections to the Internet. (demand dial-up, for example) It's also just a good idea for very large distributed sites to increase the chance that you don't have to go off to the Internet to get an IP address. (sometimes for addresses across the street!) "slave" modifies this to say to replace the list of NS records with the forwarders entry, instead of prepending to it. This is for firewalled environments, where the nameserver can't directly get out to the Internet at all. "slave" is meaningless (and invalid, in late-model BINDs) without "forwarders". "forwarders" is an entry in named.boot, and therefore applies only to the nameserver (not to resolvers). ------------------------------- Date: Mon Jan 2 13:15:13 EST 1995 Subject: Q3.3 - When is a server authoritative? Q: What criteria does a server use to determine if it is authoritative for a domain? A: In the case of BIND: 1) The server contains current data in files for the zone in question (Data must be current for secondaries, as defined in the SOA) 2) The server is told that it is authoritative for the zone, by a 'primary' or 'secondary' keyword in /etc/named.boot. 3) The server does an error-free load of the zone. Q: I have set up a DNS where there is an SOA record for the domain, but the server still does not consider itself authoritative. (I used nslookup and set server=the correct machine.) It seems to me that something is not matching up somewhere. I suspect that this is because the service provider has not given us control over the IP numbers in our own domain, and so while the machine listed has an A record for an address, there is no corresponding PTR record. A: That's possible too, but is unrelated to the first question. You need to be delegated a zone before outside people will start talking to your server. However, a server can still be authoritative for a zone even though it hasn't been delegated authority (it's just that only the people who use that as their server will see the data). A server may consider itself non-authoritative even though it's a primary if there is a syntax error in the zone (see point 3 above). Q: I always believe that it was the NS record that defined authoritative servers. A: Nope, delegation is a separate issue from authoritativeness. You can still be authoritative, but not delegated. (you can also be delegated, but not authoritative -- that's a "lame delegation") Q: We have had problems in the past from servers that were authoritative (primary or secondary) but no NS, so other thought they were not. Some resolvers get very confused when they get non- authoritative data from the primary server. A: Yes, that's a lame delegation. That's not caused by what you said, but rather by a server which is _not_ authoritative for a zone, yet someone else (the parent) is saying that a server is authoritative (via the NS records). The set of NS records in the parent zone must be a subset of the authoritative servers to avoid lame delegations. ------------------------------- Date: Fri Apr 28 13:26:37 EDT 1995 Subject: Q3.4 - underscore in host-/domainnames Q: I had a quick look on whether underscores are allowed in host- or domainnames. RFC 1033 allows them. RFC 1035 doesn't. RFC 1123 doesn't. dnswalk complains about them. Which RFC is the final authority these days? A: Actually RFC 1035 deals with names of machines or names of mail domains. i.e "_" is not permitted in a hostname or on the RHS of the "@" in local@domain. Underscore is permitted where ever the domain is NOT one of these types of addresses. In general the DNS mostly contains hostnames and mail domainnames. This will change as new resource record types for authenticating DNS queries start to appear. The latest version of 'host' checks for illegal characters in A/MX record names and the NS/MX target names. After saying all of that, remember that RFC 1123 is a Required Internet Standard (per RFC 1720), and RFC 1033 isn't. Even 1035 isn't a required standard. Therefore, RFC 1123 wins, no contest. ------------------------------- Date: Fri Dec 2 15:03:56 EST 1994 Subject: Q3.5 - Lame delegation Q: What is lame delegation ? A: Two things are required for a lame delegation: 1) A nameserver X is delegated as authoritative for a zone. 2) Nameserver X is not performing nameservice for that zone. Try to think of a lame delegation as a long-term condition, brought about by a misconfiguration somewhere. Bryan Beecher's 1992 LISA paper on lame delegations is good to read on this. The problem really lies in misconfigured nameservers, not "lameness" brought about by transient outages. The latter is common on the Internet and hard to avoid, while the former is correctable. In order to be performing nameservice for a zone, it must have (presumed correct) data for that zone, and it must be answering authoritatively to resolver queries for that zone. (The AA bit is set in the flags section) The "classic" lame delegation case is when nameserver X is delegated as authoritative for domain Y, yet when you ask Y about X, it returns non-authoritative data. Here's an example that shows what happens most often (using dig, dnswalk, and doc to find). Let's say the domain bogus.com gets registered at the NIC and they have listed 2 primary name servers, both from their *upstream* provider: bogus.com IN NS ns.bogus.com bogus.com IN NS upstream.com bogus.com IN NS upstream1.com So the root servers have this info. But when the admins at bogus.com actually set up their zone files they put something like: bogus.com IN NS upstream.com bogus.com IN NS upstream1.com So your name server may have the nameserver info cached (which it may have gotten from the root). The root says "go ask ns.bogus.com" since they are authoritative This is usually from stuff being registered at the NIC (either nic.ddn.mil or rs.internic.net), and then updated later, but the folks who make the updates later never let the folks at the NIC know about it. Q: How can I see if the server is "lame" ? A: Go to the authoritative servers one level up, and ask them who they think is authoritative, and then go ask each one of those delegees if they think that they themselves are authoritative. If any responds "no", then you know who the lame delegation is, and who is delegating lamely to them. You can then send off a message to the administrators of the level above. The 'lamers' script from Byran Beecher really takes care of all this for you. It parses the lame delegation notices from BIND's syslog and summarizes them for you. It may be found in the contrib section of the latest BIND distribution. The latest version is available for anonymous ftp from ftp://terminator.cc.umich.edu/dns/lame-delegations/ If you want to actively check for lame delegations, you can use 'doc' and 'dnswalk'. You can check things manually with 'dig'. ------------------------------- Date: Thu Dec 1 11:10:39 EST 1994 Subject: Q3.6 - What does opt-class field do? Q: Just something I was wondering about: What does the opt-class field in an name database do (the one that always says IN)? What would happen if I put something else there instead? A: This field is the address class. From the BOG - ...is the address class; currently, only one class is supported: IN for internet addresses and other internet information. Limited support is included for the HS class, which is for MIT/Athena ``Hesiod'' information. ------------------------------- Date: Fri Feb 10 14:49:54 EST 1995 Subject: Q3.7 - Top level domains A section from RFC 1591: 2. The Top Level Structure of the Domain Names In the Domain Name System (DNS) naming of computers there is a hierarchy of names. The root of system is unnamed. There are a set of what are called "top-level domain names" (TLDs). These are the generic TLDs (EDU, COM, NET, ORG, GOV, MIL, and INT), and the two letter country codes from ISO-3166. It is extremely unlikely that any other TLDs will be created. [ Ed note: the ISO-3166 country codes may be found for anonymous ftp from: ftp://ftp.isi.edu/in-notes/iana/assignments/country-codes ftp://ftp.ripe.net/iso3166-codes ] Under each TLD may be created a hierarchy of names. Generally, under the generic TLDs the structure is very flat. That is, many organizations are registered directly under the TLD, and any further structure is up to the individual organizations. In the country TLDs, there is a wide variation in the structure, in some countries the structure is very flat, in others there is substantial structural organization. In some country domains the second levels are generic categories (such as, AC, CO, GO, and RE), in others they are based on political geography, and in still others, organization names are listed directly under the country code. The organization for the US country domain is described in RFC 1480. Each of the generic TLDs was created for a general category of organizations. The country code domains (for example, FR, NL, KR, US) are each organized by an administrator for that country. These administrators may further delegate the management of portions of the naming tree. These administrators are performing a public service on behalf of the Internet community. Descriptions of the generic domains and the US country domain follow. Of these generic domains, five are international in nature, and two are restricted to use by entities in the United States. World Wide Generic Domains: COM - This domain is intended for commercial entities, that is companies. This domain has grown very large and there is concern about the administrative load and system performance if the current growth pattern is continued. Consideration is being taken to subdivide the COM domain and only allow future commercial registrations in the subdomains. EDU - This domain was originally intended for all educational institutions. Many Universities, colleges, schools, educational service organizations, and educational consortia have registered here. More recently a decision has been taken to limit further registrations to 4 year colleges and universities. Schools and 2-year colleges will be registered in the country domains (see US Domain, especially K12 and CC, below). NET - This domain is intended to hold only the computers of network providers, that is the NIC and NOC computers, the administrative computers, and the network node computers. The customers of the network provider would have domain names of their own (not in the NET TLD). ORG - This domain is intended as the miscellaneous TLD for organizations that didn't fit anywhere else. Some non- government organizations may fit here. INT - This domain is for organizations established by international treaties, or international databases. United States Only Generic Domains: GOV - This domain was originally intended for any kind of government office or agency. More recently a decision was taken to register only agencies of the US Federal government in this domain. State and local agencies are registered in the country domains (see US Domain, below). MIL - This domain is used by the US military. Example country code Domain: US - As an example of a country domain, the US domain provides for the registration of all kinds of entities in the United States on the basis of political geography, that is, a hierarchy of <entity-name>.<locality>.<state-code>.US. For example, "IBM.Armonk.NY.US". In addition, branches of the US domain are provided within each state for schools (K12), community colleges (CC), technical schools (TEC), state government agencies (STATE), councils of governments (COG),libraries (LIB), museums (MUS), and several other generic types of entities (see RFC 1480 for details). A section from RFC 1480: 2. NAMING STRUCTURE The US Domain hierarchy is based on political geography. The basic name space under US is the state name space, then the "locality" name space, (like a city, or county) then organization or computer name and so on. For example: BERKELEY.CA.US PORTLAND.WA.US There is of course no problem with running out of names. The things that are named are individual computers. If you register now in one city and then move, the database can be updated with a new name in your new city, and a pointer can be set up from your old name to your new name. This type of pointer is called a CNAME record. The use of unregistered names is not effective and causes problems for other users. Inventing your own name and using it without registering is not a good idea. In addition to strictly geographically names, some special names are used, such as FED, STATE, AGENCY, DISTRICT, K12, LIB, CC, CITY, and COUNTY. Several new name spaces have been created, DNI, GEN, and TEC, and a minor change under the "locality" name space was made to the existing CITY and COUNTY subdomains by abbreviating them to CI and CO. A detailed description follows. Below US, Parallel to States: ----------------------------- "FED" - This branch may be used for agencies of the federal government. For example: <org-name>.<city>.FED.US "DNI" - DISTRIBUTED NATIONAL INSTITUTES - The "DNI" branch was created directly under the top-level US. This branch is to be used for distributed national institutes; organizations that span state, regional, and other organizational boundaries; that are national in scope, and have distributed facilities. For example: <org-name>.DNI.US. Name Space Within States: ------------------------ "locality" - cities, counties, parishes, and townships. Subdomains under the "locality" would be like CI.<city>.<state>.US, CO.<county>.<state>.US, or businesses. For example: Petville.Marvista.CA.US. "CI" - This branch is used for city government agencies and is a subdomain under the "locality" name (like Los Angeles). For example: Fire-Dept.CI.Los-Angeles.CA.US. "CO" - This branch is used for county government agencies and is a subdomain under the "locality" name (like Los Angeles). For example: Fire-Dept.CO.San-Diego.CA.US. "K12" - This branch may be used for public school districts. A special name "PVT" can be used in the place of a school district name for private schools. For example: <school-name>.K12.<state>.US and <school-name>.PVT.K12.<state>.US. "CC" - COMMUNITY COLLEGES - This branch was established for all state wide community colleges. For example: <school-name>.CC.<state>.US. "TEC" - TECHNICAL AND VOCATIONAL SCHOOLS - The branch "TEC" was established for technical and vocational schools and colleges. For example: <school-name>.TEC.<state>.US. "LIB" - LIBRARIES (STATE, REGIONAL, CITY, COUNTY) - This branch may be used for libraries only. For example: <lib-name>.LIB.<state>.US. "STATE" - This branch may be used for state government agencies. For example: <org-name>.STATE.<state>.US. "GEN" - GENERAL INDEPENDENT ENTITY - This branch is for the things that don't fit easily into any other structure listed -- things that might fit in to something like ORG at the top-level. It is best not to use the same keywords (ORG, EDU, COM, etc.) that are used at the top-level to avoid confusion. GEN would be used for such things as, state-wide organizations, clubs, or domain parks. For example: <org-name>.GEN.<state-code>.US. The application form for the US domain may be found for anonymous ftp from: ftp://internic.net/templates/us-domain-template.txt The application form for the EDU, COM, NET, ORG, and GOV domains may be found for anonymous ftp from: ftp://internic.net/templates/domain-template.txt ------------------------------- Date: Sun Nov 27 23:32:41 EST 1994 Subject: Q3.8 - Classes of networks Q: I am just kind of curious to what exactly the differences in classes of networks are (class A, B, C). A: An Internet Protocol (IP) address is 32 bit in length, divided into two or three parts (the network address, the subnet address (if present), and the host address. The subnet addresses are only present if the network has been divided into subnetworks. The length of the network, subnet, and host field are all variable. There are five different network classes. The leftmost bits indicate the class of the network. # bits in # bits in network host Class field field Internet Protocol address in binary Ranges ============================================================================ A 7 24 0NNNNNNN.HHHHHHHH.HHHHHHHH.HHHHHHHH 1-127.x.x.x B 14 16 10NNNNNN.NNNNNNNN.HHHHHHHH.HHHHHHHH 128-191.x.x.x C 22 8 110NNNNN.NNNNNNNN.NNNNNNNN.HHHHHHHH 192-223.x.x.x D NOTE 1 1110xxxx.xxxxxxxx.xxxxxxxx.xxxxxxxx 224-239.x.x.x E NOTE 2 11110xxx.xxxxxxxx.xxxxxxxx.xxxxxxxx 240-247.x.x.x where N represents part of the network address and H represents part of the host address. When the subnet address is defined, the needed bits are assigned from the host address space. NOTE 1: Reserved for multicast groups - RFC 1112 NOTE 2: Reserved for future use 127.0.0.1 is reserved for local loopback. Under the current arrangements, many class A IP numbers will not be assigned whereas class C usage will be at a premium. ------------------------------- Date: Fri Apr 28 13:31:24 EDT 1995 Subject: Q3.9 - What is CIDR ? Q: What is CIDR ? A: CIDR is "Classless Inter-Domain Routing (CIDR). From RFC1517: ...Classless Inter-Domain Routing (CIDR) attempts to deal with these problems by defining a mechanism to slow the growth of routing tables and reduce the need to allocate new IP network numbers. Much more information may be obtained in RFCs 1467, 1517, 1518, 1520; with primary reference 1519 ------------------------------- Date: Fri Apr 28 13:31:24 EDT 1995 Subject: Q3.10 - What is the rule for glue ? Q: What is the rule for glue ? A: A glue record is an A record for a name that appears on the right-hand side of a NS record. So, if you have this: sub.foobar.com. IN NS dns.sub.foobar.com. dns.sub.foobar.com. IN A 1.2.3.4 then the second record is a glue record (for the NS record above it). You need glue records when -- and only when -- you are delegating authority to a nameserver that "lives" in the domain you are delegating *and* you aren't a secondary server for that domain. In other words, in the example above, you need to add an A record for dns.sub.foobar.com since it "lives" in the domain it serves. This boot strapping information is necessary: How are you supposed to find out the IP address of the nameserver for domain FOO if the nameserver for FOO "lives" in FOO? If you have this NS record: sub.foobar.com. IN NS dns.xyz123.com. you do NOT need a glue record, and, in fact, adding one is a very bad idea. If you add one, and then the folks at xyz123.com change the address, then you will be passing out incorrect data. Also, unless you actually have a machine called something.IN-ADDR.ARPA, you will never have any glue records present in any of your "reverse" files. There is also a sort of implicit glue record that can be useful (or confusing :^) ). If the parent server (abc.foobar.com domain in example above) is a secondary server for the child, then the A record will be fetched from the child server when the zone transfer is done. The glue is still there but it's a little different, it's in the ip address in the named.boot line instead of explicitly in the data. In this case you can leave out the explicit glue A record and leave the manually configured "glue" in just the one place in the named.boot file. RFC 1537 says it quite nicely: 2. Glue records Quite often, people put unnecessary glue (A) records in their zone files. Even worse is that I've even seen *wrong* glue records for an external host in a primary zone file! Glue records need only be in a zone file if the server host is within the zone and there is no A record for that host elsewhere in the zone file. Old BIND versions ("native" 4.8.3 and older versions) showed the problem that wrong glue records could enter secondary servers in a zone transfer. From: cdp@njit.edu (Chris Peckham) Subject: comp.protocols.tcp-ip.domains Frequently Asked Questions (FAQ) (Part 2 of 2) Originator: cdp2582@hertz.njit.edu Keywords: BIND,DOMAIN,DNS Sender: news@njit.edu Reply-To: domain-faq@njit.edu (comp.protocols.tcp-ip.domains FAQ comments) Organization: NJIT.EDU - New Jersey Institute of Technology, Newark, NJ, USA Date: Tue, 4 Jul 1995 04:17:31 GMT Expires: Tue 08 Aug 95 00:17:18 EDT Lines: 1107 Posted-By: auto-faq 3.1.1.2 Archive-name: internet/tcp-ip/domains-faq/part2 Revision: 1.5 1995/05/12 18:50:41 This FAQ is edited and maintained by Chris Peckham, <cdp@njit.edu>. The latest version may always be found for anonymous ftp from ftp://rtfm.mit.edu/pub/usenet/news.answers/internet/tcp-ip/domains-faq ftp://ftp.njit.edu/pub/dns/Comp.protocols.tcp-ip.domains.FAQ If you can contribute any answers for items in the TODO section, please do so by sending e-mail to domain-faq@njit.edu ! If you know of any items that are not included and you feel that they should be, send the relevant information to domain-faq@njit.edu. ------------------------------ Date: Fri May 12 14:41:47 EDT 1995 Subject: Table of Contents Table of Contents ================= Part 1 ------ 0. TO DO 1. INTRODUCTION / MISCELLANEOUS 1.1 What is this newsgroup ? 1.2 More information 1.3 What is BIND and where is the latest version of BIND ? 1.4 How can I find the route between systems ? 1.5 Finding the hostname if you have the tcp-ip address 1.6 How to register a domain name 1.7 Change of Domain name 1.8 How memory and CPU does DNS use ? 1.9 Other things to consider when planning your servers 1.10 Proper way to get NS and reverse IP records into DNS 1.11 How to get my address assign from NIC? 1.12 Is there a block of private IP addresses I can use? 1.13 Cache failed lookups 1.14 What does an NS record really do ? 1.15 DNS ports 1.16 Obtaining the latest cache file 2. UTILITIES 2.1 Utilities to administer DNS zone files 2.2 DIG - Domain Internet Groper 2.3 DNS packet analyzer 2.4 host 2.5 Programming with DNS 2.6 A source of information relating to DNS 3. DEFINITIONS 3.1 TCP/IP Host Naming Conventions 3.2 Slaves and servers with forwarders 3.3 When is a server authoritative? 3.4 Underscore in host-/domain names 3.5 Lame delegation 3.6 What does opt-class field do? 3.7 Top level domains 3.8 Classes of networks 3.9 What is CIDR ? 3.10 What is the rule for glue ? Part 2 ------ 4. CONFIGURATION 4.1 Changing a Secondary server to a Primary 4.2 How do I subnet a Class B Address ? 4.3 Subnetted domain name service 4.4 Recommended format/style of DNS files 4.5 DNS on a system not connected to the Internet 4.6 Multiple Domain configuration 4.7 wildcard MX records 4.8 How to identify a wildcard MX record 4.9 Why are fully qualified domain names recommended ? 4.10 Distributing load using named 4.11 Order of returned records 4.12 resolv.conf 4.13 Delegating authority 4.14 DNS instead of NIS on a Sun OS 4.1.x system 5. PROBLEMS 5.1 No address for root server 5.2 Error - No Root Nameservers for Class XX 5.3 Bind 4.9.x and MX querying? 5.4 Some root nameservers don't know localhost 5.5 MX records and CNAMES and separate A records for MX targets 5.6 NS is a CNAME 5.7 Nameserver forgets own A record 5.8 General problems (core dumps !) 5.9 malloc and DECstations 6. ACKNOWLEDGEMENTS ------------------------------ Date: Fri Dec 2 15:31:06 EST 1994 Subject: Q4.1 - Changing a Secondary server to a Primary Q: Do I need to do anything special when I change a server from a secondary to a primary ? A: For 4.8.3, it's prudent to kill and restart following any changes to named.boot. In BIND 4.9.3, you only have to kill and restart named if you change a primary zone to a secondary or v-v, or if you delete a zone and remain authoritative for its parent. Every other case should be taken care of by a HUP. (Ed. note: 4.9.3b9 may still require you to kill and restart the server due to some bugs in the HUP code). You will also need to update the server information on the root servers. You can do this by filing a new domain registration form to inform InterNIC of the change. They will then update the root server's SOA records. This process usually takes 10-12 business days after they receive the request. ------------------------------- Date: Fri Apr 28 13:34:52 EDT 1995 Subject: Q4.2 - How do I subnet a Class B Address ? Q: I just received a Class B internet address and I am wondering where to get an RFC or other information on how to properly to the TCP/IP sub-netting. A: That you need to subnet at all is something of a misconception. You can also think of a class B network as giving you 65,534 individual hosts, and such a network will work. You can also configure your class B as 16,384 networks of 2 hosts each. That's obviously not very practical, but it needs to be made clear that you are not constrained by the size of an octet (remember that many older devices would not work in a network configured in this manner). So, the question is: why do you need to subnet? One reason is that it is easier to manage a subnetted network, and in fact, you can delegate the responsibility for address space management to local administrators on the various subnets. Also, IP based problems will end up localized rather than affecting your entire network. If your network is a large backbone with numerous segments individually branching off the backbone, that too suggests subnetting. Subnetting can also be used to improve routing conditions. You may wish to partition your network to disallow certain protocols on certain segments of your net. You can, for example, restrict IP or IPX to certain segments only by adding a router routing high level protocols, and across the router you may have to subnet. Finally, as far as how many subnets you need depends on the answer to the above question. As far as subnet masks are concerned, the mask can be anything from 255.0.0.0 to 255.255.255.252. You'll probably be looking at 9 or 10 bits for the subnet (last octet 128 or 192 respectively). RFC1219 discusses the issue of subnetting very well and leaves the network administrator with a large amount of flexibility for future growth. ------------------------------ Date: Sun Nov 27 23:32:41 EST 1994 Subject: Q4.3 -Subnetted domain name service Q: After doing some reading (DNS and BIND, Albitz&Liu), I don't really find any examples of handling subnetted class C networks as separate DNS domains. A: This is possible, just messy. You need to delegate down to the fourth octet, so you will have one domain per IP address ! Here is how you can subdelegate a in-addr.arpa address for non-byte aligned subnet masks: Take as an example the net 192.1.1.x, and example subnet mask 255.255.255.240. We first define the domain for the class C net, $origin 1.1.192.in-addr.arpa @ SOA (usual stuff) @ ns some.nameserver ns some.other.nameserver ; delegate a subdomain one ns one.nameserver ns some.nameserver ; delegate another two ns two.nameserver ns some.nameserver ; CNAME pointers to subdomain one 0 CNAME 0.one 1 CNAME 1.one ; through 15 CNAME 15.one ; CNAME pointers to subdomain two 16 CNAME 16.two 17 CNAME 17.two 31 CNAME 31.two ; CNAME as many as required. Now, in the delegated nameserver, one.nameserver $origin one.1.1.192.in-addr.arpa @ SOA (usual stuff) NS one.nameserver NS some.nameserver ; secondary for us 0 PTR onenet.one.domain 1 PTR onehost.one.domain ; through 15 PTR lasthost.one.domain And similar for the two.1.1.192.in-addr.arpa delegated domain. ------------------------------ Date: Sun Nov 27 23:32:41 EST 1994 Subject: Q4.4 - Recommended format/style of DNS files Q: Are there any suggestions for how to layout DNS configuration files (both forward and reverse)? A: This answer is quoted from an article posted by Paul Vixie: I've gone back and forth on the question of whether the BOG should include a section on this topic. I know what I myself prefer, but I'm wary of ramming my own stylistic preferences down the throat of every BOG reader. But since you ask :-)... Create /var/named. If your system is too old to have a /var, either create one or use /usr/local/adm/named instead. Put your named.boot in it, and make /etc/named.boot a symlink to it. If your system doesn't have symlinks, you're S-O-L (but you knew that). In named.boot, put a "directory" directive that specifies your actual BIND working directory: directory /var/named All relative pathnames used in "primary", "secondary", and "cache" directives will be evaluated relative to this directory. Create two subdirectories, /var/named/pri and /var/named/sec. Whenever you add a "primary" directive to your named.boot, use "pri/WHATEVER" as the path name. And then put the primary zone file into "pri/WHATEVER". Likewise when you add "secondary" directives, use "sec/WHATEVER" and BIND (really named-xfer) will create the files in that subdirectory. (Variations: (1) make a midlevel directory "zones" and put "pri" and "sec" into it; (2) if you tend to pick up a lot of secondaries from a few hosts, group them together in their own subdirectories -- something like /var/named/zones/uucp if you're a UUCP Project name server.) For your forward files, name them after the zone. dec.com becomes "/var/named/zones/pri/dec.com". For your reverse files, name them after the network number. 0.1.16.in-addr.arpa becomes "/var/named/zones/pri/16.1.0". When creating or maintaining primary zone files, try to use the same SOA values everywhere, except for the serial number which varies per zone. Put a $ORIGIN directive at the top of the primary zone file, not because its needed (it's not since the default origin is the zone named in the "primary" directive) but because it make it easier to remember what you're working on when you have a lot of primary zones. Put some comments up there indicating contact information for the real owner if you're proxying. Use RCS and put the "Id" in a ";" comment near the top of the zone file. The SOA and other top level information should all be listed together. But don't put IN on every line, it defaults nicely. For example: ============== @ IN SOA gw.home.vix.com. postmaster.vix.com. ( 1994082501 ; serial 3600 ; refresh (1 hour) 1800 ; retry (30 mins) 604800 ; expire (7 days) 3600 ) ; minimum (1 hour) NS gw.home.vix.com. NS ns.uu.net. NS uucp-gw-1.pa.dec.com. NS uucp-gw-2.pa.dec.com. MX 10 gw.home.vix.com. MX 20 uucp-gw-1.pa.dec.com. MX 20 uucp-gw-1.pa.dec.com. ============== I don't necessarily recommend those SOA values. Not every zone is as volatile as the example shown. I do recommend that serial number format; it's in date format with a 2-digit per-day revision number. This format will last us until 2147 A.D. at which point I expect a better solution will have been found :-). (Note that it would last until 4294 A.D. except that there are some old BINDs out there that use a signed quantity for representing serial number interally; I suppose that as long as none of these are still running after 2047 A.D., that we can use the above serial number format until 4294 A.D., at which point a better solution will HAVE to be found.) You'll note that I use a tab stop for "IN" even though I never again specify it. This leaves room for names longer than 7 bytes without messing up the columns. You might also note that I've put the MX priority and destination in the same tab stop; this is because both are part of the RRdata and both are very different from MX which is an RRtype. Some folks seem to prefer to group "MX" and the priority together in one tab stop. While this looks neat it's very confusing to newcomers and for them it violates the law of least astonishment. If you have a multi-level zone (one which contains names that have dots in them), you can use additional $ORIGIN statements but I recommend against it since there is no "back" operator. That is, given the above example you can add: ============= $ORIGIN home gw A 192.5.5.1 ============= The problem with this is that subsequent RR's had better be somewhere under the "home.vix.com" name or else the $ORIGIN that introduces them will have to use a fully qualified name. FQDN $ORIGIN's aren't bad and I won't be mad if you use them. Unqualified ones as shown above are real trouble. I usually stay away from them and just put the whole name in: ============= gw.home A 192.5.5.1 ============= In your reverse zones, you're usually in some good luck because the owner name is usually a single short token or sometimes two. ============= $ORIGIN 5.5.192.in-addr.arpa. @ IN SOA ... NS ... 1 PTR gw.home.vix.com. ========================================= $ORIGIN 1.16.in-addr.arpa. @ IN SOA ... NS ... 2.0 PTR gatekeeper.dec.com. ============= It is usually pretty hard to keep your forward and reverse zones in synch. You can avoid that whole problem by just using "h2n" (see the ORA book, DNS and BIND, and its sample toolkit, included in the BIND distribution or on ftp.uu.net (use the QUOTE SITE EXEC INDEX command there to find this -- I never can remember where it's at). "h2n" and many tools like it can just read your old /etc/hosts file and churn it into DNS zone files. (May I recommend contrib/decwrl/mkdb.pl from the BIND distribution?) However, if you (like me) prefer to edit these things by hand, you need to follow the simple convention of making all of your holes consistent. If you use 192.5.5.1 and 192.5.5.3 but not (yet) 192.5.5.2, then in your forward file you will have something like ============= ... gw.home A 192.5.5.1 ;avail A 192.5.5.2 pc.home A 192.5.5.3 ============= and in your reverse file you will have something like ============= ... 1 PTR gw.home.vix.com. ;2 PTR avail 3 PTR pc.home.vix.com. ============= This convention will allow you to keep your sanity and make fewer errors. Any kind of automation (h2n, mkdb, or your own perl/tcl/awk/python tools) will help you maintain a consistent universe even if it's also a complex one. Editing by hand doesn't have to be deadly but you MUST take care. ------------------------------ Date: Sun Nov 27 23:32:41 EST 1994 Subject: Q4.5 - DNS on a system not connected to the Internet Q: How do I use DNS on a system that is not connected to the Internet or set BIND up with an internal root server ? A: You need to create your own root domain name server until you connect to the internet. Your roots need to delegate to mydomain.com and any in-addr.arpa subdomains you might have, and that's about it. As soon as you're connected, rip out the fake roots and use the real ones. It does not actually have to be another server pretending to be the root. You can set up the name server so that it is primary for each domain above you and leave them empty (i.e. you are foo.bar.com - claim to be primary for bar.com and com) Q: What if you connect intermittently and want DNS to work when you are connected, and "fail" when you are not ? A: You can point the resolver at the name server at the remote site and if the connection (SLIP/PPP) isn't up, the resolver doesn't have a route to the remote server and since there's only one name server in resolv.conf, the resolver quickly backs off the using /etc/hosts. No problem. You could do the same with multiple name server and a resolver that did configurable /etc/hosts fallback. ------------------------------ Date: Fri Dec 2 15:40:49 EST 1994 Subject: Q4.6 -Multiple Domain configuration Q: I have seen sites that seem to have multiple domain names pointing to the same destination. I would like to implement this and have found no information explaining how to do it. What I would like to do is: ftp ftp.biff.com connects user to -> ftp.biff.com ftp ftp.fred.com connects user to -> ftp.biff.com ftp ftp.bowser.com connects user to -> ftp.biff.com A: This is done through CNAME records: ftp.bowser.com. IN CNAME ftp.biff.com. You can also do the same thing with multiple A records. ------------------------------ Date: Sun Nov 27 23:32:41 EST 1994 Subject: Q4.7 - wildcard MX records Q: Does BIND not understand wildcard MX records such as the following? *.foo.com MX 0 mail.foo.com. A: Explicit RR's at one level of specificity will, by design, "block" a wildcard at a lesser level of specificity. I suspect that you have an RR (an A RR, perhaps?) for "bar.foo.com" which is blocking the application of your "*.foo.com" wildcard. The initial MX query is thus failing (NOERROR but an answer count of 0), and the backup query finds the A RR for "bar.foo.com" and uses it to deliver the mail directly (which is what you DIDN'T want it to do). Adding an explicit MX RR for the host is therefore the right way to handle this situation. See RFC 1034, Section 4.3.3 ("Wildcards") for more information on this "blocking" behavior, along with an illustrative example. See also RFC 974 for an explanation of standard mailer behavior in the face of an "empty" response to one's MX query. Basically, what it boils down to is, there is no point in trying to use a wildcard MX for a host which is otherwise listed in the DNS. It just doesn't work. ------------------------------ Date: Thu Dec 1 11:10:39 EST 1994 Subject: Q4.8 - How to identify a wildcard MX record Q: How do you identify a wildcard MX record ? A: You don't really need to "identify" a wildcard MX RR. The precedence for u@dom is: exact match MX exact match A wildcard MX One way to implement this is to query for ("dom",IN,MX) and if the answer name that comes back is "*." something, you know it's a wildcard, therefore you know there is no exact match MX, and you therefore query for ("dom",IN,A) and if you get something, use it. if you don't, use the previous wildcard response. RFC 974 explains this pretty well. ------------------------------ Date: Sun Nov 27 23:32:41 EST 1994 Subject: Q4.9 - Why are fully qualified domain names recommended ? Q: Why are fully qualified domain names recommended ? A: The documentation for BIND 4.9.2 says that the hostname should be set to the full domain style name (i.e host.our.domain rather than host). What advantages are there in this, and are there any adverse consequences if we don't? A: Paul Vixie likes to do it :-) He lists a few reasons - * Sendmail can be configured to just use Dj$w rather than Dj$w.mumble where "mumble" is something you have to edit in by hand. Granted, most people use "mumble" elsewhere in their config files ("tack on local domain", etc) but why should it be a requirement ? * The real reason is that not doing it violates a very useful invariant: gethostbyname(gethostname) == gethostbyaddr(primary_interface_address) If you take an address and go "backwards" through the PTR's with it, you'll get a FQDN, and if you push that back through the A RR's, you get the same address. Or you should. Many multi-homed hosts violate this uncaringly. If you take a non-FQDN hostname and push it "forwards" through the A RR's, you get an address which, if you push it through the PTR's, comes back as a FQDN which is not the same as the hostname you started with. Consider the fact that, absent NIS/YP, there is no "domainname" command analogous to the "hostname" command. (NIS/YP's doesn't count, of course, since it's sometimes-but-only-rarely the same as the Internet domain or subdomain above a given host's name.) The "domain" keyword in resolv.conf doesn't specify the parent domain of the current host; it specifies the default domain of queries initiated on the current host, which can be a very different thing. (As of RFC 1535 and BIND 4.9.2's compliance with it, most people use "search" in resolv.conf, which overrides "domain", anyway.) What this means is that there is NO authoritative way to programmatically discover your host's FQDN unless it is set in the hostname, or unless every application is willing to grovel the "netstat -in" tables, find what it hopes is the primary address, and do a PTR query on it. FQDN /bin/hostnames are, intuitively or not, the simplest way to go. ------------------------------ Date: Wed Mar 1 11:04:43 EST 1995 Subject: Q4.10 - Distributing load using named Q: If you attempt to distribute the load on a system using named, won't the first response be cached, and then later queries use the cached value? (This would be for requests that come through the same server.) A: Yes. So it can be useful to use a lower TTL on records where this is important. You can use values like 300 or 500 seconds. If your local caching server has ROUND_ROBIN, it does not matter what the authoritative servers have -- every response from the cache is rotated. But if it doesn't, and the authoritative server site is depending on this feature (or the old "shuffle-A") to do load balancing, then if one doesn't use small TTLs, one could conceivably end up with a really nasty situation, e.g., hundreds of workstations at a branch campus pounding on the same front end at the authoritative server's site during class registration. Not nice. A: Paul Vixie has an example of the ROUND_ROBIN code in action. Here is something that he wrote regarding his example: >I want users to be distributed evenly among those 3 hosts. Believe it or not :-), BIND offers an ugly way to do this. I offer for your collective amusement the following snippet from the ugly.vix.com zone file: hydra cname hydra1 cname hydra2 cname hydra3 hydra1 a 10.1.0.1 a 10.1.0.2 a 10.1.0.3 hydra2 a 10.2.0.1 a 10.2.0.2 a 10.2.0.3 hydra3 a 10.3.0.1 a 10.3.0.2 a 10.3.0.3 Note that having multiple CNAME RR's at a given name is meaningless according to the DNS RFCs but BIND doesn't mind (in fact it doesn't even complain). If you call gethostbyname("hydra.ugly.vix.com") (try it!) you will get results like the following. Note that there are two round robin rotations going on: one at ("hydra",CNAME) and one at each ("hydra1",A) et al. I used a layer of CNAME's above the layer of A's to keep the response size down. If you don't have nine addresses you probably don't care and would just use a pile of CNAME's pointing directly at real host names. {hydra.ugly.vix.com} name: hydra2.ugly.vix.com aliases: hydra.ugly.vix.com addresses: 10.2.0.2 10.2.0.3 10.2.0.1 {hydra.ugly.vix.com} name: hydra3.ugly.vix.com aliases: hydra.ugly.vix.com addresses: 10.3.0.2 10.3.0.3 10.3.0.1 {hydra.ugly.vix.com} name: hydra1.ugly.vix.com aliases: hydra.ugly.vix.com addresses: 10.1.0.2 10.1.0.3 10.1.0.1 {hydra.ugly.vix.com} name: hydra2.ugly.vix.com aliases: hydra.ugly.vix.com addresses: 10.2.0.3 10.2.0.1 10.2.0.2 {hydra.ugly.vix.com} name: hydra3.ugly.vix.com aliases: hydra.ugly.vix.com addresses: 10.3.0.3 10.3.0.1 10.3.0.2 ------------------------------ Date: Sun Dec 4 22:12:32 EST 1994 Subject: Q4.11 - Order of returned records Q: Is there any way to tell named to return records, specifically address records, in the order in which they are listed in the database? It would appear that named consistently applies a sorting algorithm to address records which seems to be virtually guaranteed to be pessimal for our routers, which have many A records. A: Sorting, is the *resolver's* responsibility. RFC 1123: 6.1.3.4 Multihomed Hosts When the host name-to-address function encounters a host with multiple addresses, it SHOULD rank or sort the addresses using knowledge of the immediately connected network number(s) and any other applicable performance or history information. DISCUSSION: The different addresses of a multihomed host generally imply different Internet paths, and some paths may be preferable to others in performance, reliability, or administrative restrictions. There is no general way for the domain system to determine the best path. A recommended approach is to base this decision on local configuration information set by the system administrator. In BIND 4.9.x's resolver code, the "sortlist" directive in resolv.conf can be used to configure this. ------------------------------ Date: Fri Feb 10 15:46:17 EST 1995 Subject: Q4.12 - resolv.conf Q: Why should I use "real" IP addresses in /etc/resolv.conf and not 0.0.0.0 or 127.0.0.1. A: Paul Vixie writes on the issue of the contents of resolv.conf: It's historical. Some kernels can't unbind a UDP socket's source address, and some resolver versions (notably not including BIND 4.9.2 or 4.9.3's) try to do this. The result can be wide area network traffic with 127.0.0.1 as the source address. Rather than giving out a long and detailed map of version/vendor combinations of kernels/BINDs that have/don't this problem, I just tell folks not to use 127.0.0.1 at all. 0.0.0.0 is just an alias for the first interface address assigned after a system boot, and if that interface is a up-and-down point to point link (PPP, SLIP, whatever), there's no guarantee that you'll be able to reach yourself via 0.0.0.0 during the entire lifetime of any system instance. On most kernels you can finesse this by adding static routes to 127.0.0.1 for each of your interface addresses, but some kernels don't like that trick and rather than give a detailed map of which ones work and which ones don't, I just globally recommend against 0.0.0.0. If you know enough to know that 127.0.0.1 or 0.0.0.0 is safe on your kernel and resolver, then feel free to use them. If you don't know for sure that it is safe, don't use them. I never use them (except on my laptop, whose hostname is "localhost" and whose 0.0.0.0 is 127.0.0.1 since I ifconfig my lo0 before any other interface). The operational advantage to using a real IP address rather than an wormhole like 0.0.0.0 or 127.0.0.1, is that you can then "rdist" or otherwise share identical copies of your resolv.conf on all the systems on any given subnet, not all of which will be servers. A: The problem was with older versions of the resolver (4.8.X). If you listed 127.0.0.1 as the first entry in resolv.conf, and for whatever reason the local name server wasn't running and the resolver fell back to the second name server listed, it would send queries to the name server with the source IP address set to 127.0.0.1 (as it was set when the resolver was trying to send to 127.0.0.1--you use the loopback address to send to the loopback address). ------------------------------ Date: Mon Jan 2 13:50:13 EST 1995 Subject: Q4.13 - Delegating authority Q: How do I delegate authority for domains within my domain ? A: When you start having a very big domain that can be broken into logical and separate entities that can look after their own DNS information, you will probably want to do this. Maintain a central area for the things that everyone needs to see and delegate the authority for the other parts of the organization so that they can manage themselves. Another essential piece of information is that every domain that exists must have it NS records associated with it. These NS records denote the name servers that are queried for information about that zone. For your zone to be recognized by the outside world, the server responsible for the zone above you must have created a NS record for your machine in your domain. For example, putting the computer club onto the network and giving them control over their own part of the domain space we have the following. The machine authorative for gu.uwa.edu.au is mackerel and the machine authorative for ucc.gu.uwa.edu.au is marlin. in mackerel's data for gu.uwa.edu.au we have the following @ IN SOA ... IN A 130.95.100.3 IN MX mackerel.gu.uwa.edu.au. IN MX uniwa.uwa.edu.au. marlin IN A 130.95.100.4 ucc IN NS marlin.gu.uwa.edu.au. IN NS mackerel.gu.uwa.edu.au. Marlin is also given an IP in our domain as a convenience. If they blow up their name serving there is less that can go wrong because people can still see that machine which is a start. You could place "marlin.ucc" in the first column and leave the machine totally inside the ucc domain as well. The second NS line is because mackerel will be acting as secondary name server for the ucc.gu domain. Do not include this line if you are not authorative for the information included in the sub-domain. ------------------------------ Date: Wed Mar 1 11:45:00 EST 1995 Subject: Q4.14 - DNS instead of NIS on a Sun OS 4.1.x system Q: I would appreciate any comments on whether running bind 4.9.x will enable sendmail, ftp, telnet and other TCP/IP services to bypass NIS and connect directly to named. A: How to do this is documented quite well in the comp.sys.sun.admin FAQ in questions one and two. You can get them from: ftp://thor.ece.uc.edu/pub/sun-faq/FAQs/sun-faq.general http://www.cis.ohio-state.edu/hypertext/faq/usenet/comp-sys-sun-faq as well as from rtfm.mit.edu in the usual place, etc. ------------------------------ Date: Mon Jan 2 13:49:43 EST 1995 Subject: Q5.1 - No address for root server Q: I've been getting the following messages lately from bind-4.9.2.. ns_req: no address for root server We are behind a firewall and have the following for our named.cache file - ; list of servers . 99999999 IN NS POBOX.FOOBAR.COM. 99999999 IN NS FOOHOST.FOOBAR.COM. foobar.com. 99999999 IN NS pobox.foobar.com. A: You can't do that. Your nameserver contacts POBOX.FOOBAR.COM, gets the correct list of root servers from it, then tries again and fails because of your firewall. You will need a 'forwarder' definition, to ensure that all requests are forwarded to a host which can penetrate the firewall. And it is unwise to put phony data into 'named.cache'. ------------------------------ Date: Sun Nov 27 23:32:41 EST 1994 Subject: Q5.2 - Error - No Root Nameservers for Class XX Q: I've received errors before about "No root nameservers for class XX" but they've been because of network connectivity problems. I believe that Class 1 is Internet Class data. And I think I heard someone say that Class 4 is Hesiod?? Does anyone know what the various Class numbers are? A: From RFC 1700: DOMAIN NAME SYSTEM PARAMETERS The Internet Domain Naming System (DOMAIN) includes several parameters. These are documented in [RFC1034] and [RFC1035]. The CLASS parameter is listed here. The per CLASS parameters are defined in separate RFCs as indicated. Domain System Parameters: Decimal Name References -------- ---- ---------- 0 Reserved [PM1] 1 Internet (IN) [RFC1034,PM1] 2 Unassigned [PM1] 3 Chaos (CH) [PM1] 4 Hesoid (HS) [PM1] 5-65534 Unassigned [PM1] 65535 Reserved [PM1] DNS information for RFC 1700 was taken from ftp://ftp.isi.edu/in-notes/iana/assignments/dns-parameters Hesiod is class 4, and there are no official root nameservers for class 4, so you can safely declare yourself one if you like. You might want to put up a packet filter so that no one outside your network is capable of making Hesiod queries of your machines, if you define yourself to be a root nameserver for class 4. ------------------------------ Date: Sun Nov 27 23:32:41 EST 1994 Subject: Q5.3 - Bind 4.9.x and MX querying? Q: If I query a 4.9.x DNS server for MX records, a list of the MX records as well as a list of the authorative nameservers is returned. Why ? A: Bind 4.9.2 returns the list of nameserver that are authorative for a domain in the response packet, along with their IP addresses in the additional section. ------------------------------ Date: Sun Nov 27 23:32:41 EST 1994 Subject: Q5.4 - Some root nameservers don't know localhost Q: Do I need to define an A record for localhost ? Where is the A record for 127.0.0.1 defined? I see where the PTR record is defined pointing to localhost, but can't find where the A record is. And is the A record supposed to be localhost.MY_DOMAIN or just localhost ? A: Somewhere deep in the BOG (BIND Operations Guide) that came with 4.9.3b9, it says that you define this yourself (if need be) in the same zone files as your "real" IP addresses for your domain (both as forward and reverse) and that you should specifically use "localhost." instead of "localhost.my.dom.ain". The reason for this was that the trailing "." will get stripped when passed back to anyone who asks this question of your nameserver, and they should then tack on the proper domain name when the go "forward" from there. In addition, anyone mis-configured to point to you (and your domain) from another domain would be putting on their domain based on this information, and not whatever you might happen to hand them. Some HP boxen (especially those running HP OpenView) will also need "loopback" defined with this IP address. You may set it as a CNAME record pointing to the "localhost." record. ------------------------------ Date: Sun Nov 27 23:32:41 EST 1994 Subject: Q5.5 - MX records and CNAMES and separate A records for MX targets Q: The O'Reilly "DNS and Bind" book warns against using non-canonical names in MX records, however, this warning is given in the context of mail hubs that MX to each other for backup purposes. I don't see how this applies to mail spokes. RFC 974 has a similar warning, but I can not see where it specifically prohibits using an alias in an MX record. A: Without the restrictions in the RFC, a MTA must request the A records for every MX listed to determine if it is in the MX list then reduce the list. This introduces many more lookups than would other wise be required. If you are behind a 1200 bps link YOU DON'T WANT TO DO THIS. The addresses associated with CNAMES are not passed as additional data so you will force additional traffic to result even if you are running a caching server locally. There is also the problem of how does the MTA find all of it's IP addresses. This is not straight forward. You have to be able to do this is you allow CNAMEs (or extra A's) as MX targets. The letter of the law is that an MX record should point to an A record. There is no "real" reason to use CNAMEs for MX targets or separate As for nameservers any more. CNAMEs for services other than mail should be used because there is no specified method for locating the desired server yet. People don't care what the names of MX targets are. They're invisible to the process anyway. If you have mail for "mary" redirected to "sue" is totally irrelevant. Having CNAMEs as the targets of MX's just needlessly complicates things, and is more work for the resolver. Having separate A's for nameservers like "ns.your.domain" is pointless too, since again nobody cares what the name of your nameserver is, since that too is invisible to the process. If you move your nameserver from "mary.your.domain" to "sue.your.domain" nobody need care except you and your parent domain administrator (and the InterNIC). Even less so for mail servers, since only you are affected. Q: Given the example - hello in cname realname mailx in mx 0 hello Now, while reading the operating manual of bind it clearly states that this is *not* valid. These two statements clearly contradict each other. Is there some later rfc than 974 that overrides what is said in there with respect to MX and CNAMEs? Anyone have the reference handy? A: This isn't what the BOG says at all. See below. You can have a CNAME that points to some other RR type; in fact, all CNAMEs have to point to other names (Canonical ones, hence the C in CNAME). What you can't have is an MX that points to a CNAME. MX RR's that point to names which have only CNAME RR's will not work in many cases, and RFC 974 intimates that it's a bad idea: Note that the algorithm to delete irrelevant RRs breaks if LOCAL has a alias and the alias is listed in the MX records for REMOTE. (E.g. REMOTE has an MX of ALIAS, where ALIAS has a CNAME of LOCAL). This can be avoided if aliases are never used in the data section of MX RRs. Here's the relevant BOG snippet: aliases {ttl} addr-class CNAME Canonical name ucbmonet IN CNAME monet The Canonical Name resource record, CNAME, speci- fies an alias or nickname for the official, or canonical, host name. This record should be the only one associated with the alias name. All other resource records should be associated with the canonical name, not with the nickname. Any resource records that include a domain name as their value (e.g., NS or MX) must list the canoni- cal name, not the nickname. ------------------------------ Date: Wed Mar 1 11:14:10 EST 1995 Subject: Q5.6 - NS is a CNAME Q: Can I do this ? Is it legal ? @ SOA (.........) NS ns.host.this.domain. NS second.host.another.domain. ns CNAME third third IN A xxx.xxx.xxx.xxx A: No. Only one RR type is allowed to refer, in its data field, to a CNAME, and that's CNAME itself. So CNAMEs can refer to CNAMEs but NSs and MXs cannot. BIND 4.9.3 (Beta11 and later) explicitly syslogs this case rather than simply failing as pre-4.9 servers did. Here's a current example: Dec 7 00:52:18 gw named[17561]: \ "foobar.com IN NS" points to a CNAME (foobar.foobar.com) Here is the reason why: Nameservers are not required to include CNAME records in the Additional Info section returned after a query. It's partly an implementation decision and partly a part of the spec. The algorithm described in RFC 1034 (pp24,25; info also in RFC 1035, section 3.3.11, p 18) says 'Put whatever addresses are available into the additional section, using glue RRs [if necessary]'. Since NS records are speced to contain only primary names of hosts, not CNAMEs, then there's no reason for algorithm to mention them. If, on the other hand, it's decided to allow CNAMEs in NS records (and indeed in other records) then there's no reason that CNAME records might not be included along with A records. The Additional Info section is intended for any information that might be useful but which isn't strictly the answer to the DNS query processed. It's an implementation decision in as much as some servers used to follow CNAMEs in NS references. ------------------------------ Date: Fri Dec 2 16:17:31 EST 1994 Subject: Q5.7 - Nameserver forgets own A record Q: Lately, I've been having trouble with named 4.9.2 and 4.9.3. Periodically, the nameserver will seem to "forget" its own A record, although the other information stays intact. One theory I had was that somehow a site that the nameserver was secondary for was "corrupting" the A record somehow. A: This is invariably due to not removing ALL of the cached zones when you moved to 4.9.X. Remove ALL cached zones and restart your nameservers. You get "ignoreds" because the primaries for the relevant zones are running old versions of BIND which pass out more glue than is required. named-xfer trims off this extra glue. ------------------------------ Date: Sun Dec 4 22:21:22 EST 1994 Subject: Q5.8 - General problems (core dumps !) Q: I am running bind 4.9.3b9p1 on a DEC alpha OSF/1 V3.0 and have had it core dump while in debug mode. The last lines printed to named.run were [...] A: Paul Vixie says: I'm always interested in hearing about cases where BIND dumps core. However, I need a stack trace. Compile with -g and not -O (unless you are using gcc and know what you are doing) and then when it dumps core, get into dbx or gdb using the executable and the core file and use "bt" to get a stack trace. Send it to me <paul@vix.com> along with specific circumstances leading to or surrounding the crash (test data, tail of the debug log, tail of the syslog... whatever matters) and ideally you should save your core dump for a day or so in case I have questions you can answer via gdb/dbx. ------------------------------ Date: Mon Jan 2 14:19:22 EST 1995 Subject: Q5.9 - malloc and DECstations We have replaced malloc on our DECstations with a malloc that is more compact in memory usage, and this helped the operation of bind a lot. The source is now available for anonymous ftp from ftp://ftp.cs.wisc.edu/pub/misc/malloc.tar.gz ------------------------------ Date: Fri Apr 28 13:56:32 EDT 1995 Subject: Q6 - Acknowledgements Listed in e-mail address alphabetical order, the following people have contributed to this FAQ: Benoit.Grange@inria.fr (Benoit.Grange) D.T.Shield@csc.liv.ac.uk (Dave Shield) adam@comptech.demon.co.uk (Adam Goodfellow) andras@is.co.za (Andras Salamon) barmar@nic.near.net (Barry Margolin) barr@pop.psu.edu (David Barr) bj@herbison.com (B.J. Herbison) bje@cbr.fidonet.org (Ben Elliston) brad@birch.ims.disa.mil (Brad Knowles) ckd@kei.com (Christopher Davis) cdp@hertz.njit.edu (Chris Peckham) cricket@hp.com (Cricket Liu) cudep@csv.warwick.ac.uk (Ian 'Vato' Dickinson [ID17]) dparter@cs.wisc.edu (David Parter) e07@nikhef.nl (Eric Wassenaar) fwp@CC.MsState.Edu (Frank Peters) gah@cco.caltech.edu (Glen A. Herrmannsfeldt) glenn@popco.com (Glenn Fleishman) harvey@indyvax.iupui.edu (James Harvey) hubert@cac.washington.edu (Steve Hubert) jmalcolm@uunet.uu.net (Joseph Malcolm) jhawk@panix.com (John Hawkinson) kevin@cfc.com (Kevin Darcy) lamont@abstractsoft.com (Sean T. Lamont) lavondes@tidtest.total.fr (Michel Lavondes) mark@ucsalf.ac.uk (Mark Powell) marka@syd.dms.CSIRO.AU (Mark Andrews) mathias@unicorn.swi.com.sg (Mathias Koerber) mjo@iao.ford.com (Mike O'Connor) nick@flapjack.ieunet.ie (Nick Hilliard) patrick@oes.amdahl.com (Patrick J. Horgan) ph10@cus.cam.ac.uk (Philip Hazel) rv@seins.Informatik.Uni-Dortmund.DE (Ruediger Volk) tanner@george.arc.nasa.gov (Rob Tanner) vixie@vix.com (Paul A Vixie) wag@swl.msd.ray.com (William Gianopoulos {84718}) whg@inel.gov (Bill Gray) wolf@pasteur.fr (Christophe Wolfhugel) Thank you !