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host(1) host(1) NNAAMMEE host - query nameserver about domain names and zones SSYYNNOOPPSSIISS hhoosstt [--vv] [--aa] [--tt _q_u_e_r_y_t_y_p_e] [_o_p_t_i_o_n_s] _n_a_m_e [_s_e_r_v_e_r] hhoosstt [--vv] [--aa] [--tt _q_u_e_r_y_t_y_p_e] [_o_p_t_i_o_n_s] --ll _z_o_n_e [_s_e_r_v_e_r] hhoosstt [--vv] [_o_p_t_i_o_n_s] --HH [--DD] [--EE] [--GG] _z_o_n_e hhoosstt [--vv] [_o_p_t_i_o_n_s] --CC _z_o_n_e hhoosstt [--vv] [_o_p_t_i_o_n_s] --AA _h_o_s_t hhoosstt [_o_p_t_i_o_n_s] --xx [_n_a_m_e ...] hhoosstt [_o_p_t_i_o_n_s] --XX _s_e_r_v_e_r [_n_a_m_e ...] OOPPTTIIOONN SSYYNNTTAAXX Besides the traditional short options (one letter with single dash, and an optional value as separate argument), there are now also long options in the format ----kkeeyy wwoorrdd[=_v_a_l_u_e]. Many (but not all) short options have a long equivalent. There are several long options without a short equivalent. The long options are not yet documented in this manual page, but a summary of the existing long options, and the mapping to their short alternative, is available via the command hhoosstt ----hheellpp. DDEESSCCRRIIPPTTIIOONN _h_o_s_t 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 information 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 --tt, --aa and --vv options, it can be used to find all of the information about domain names that is maintained by the domain name server system. The information printed consists of vari ous fields of the associated resource records that were retrieved. The arguments can be either host names (domain names) or numeric Internet addresses. A numeric Internet address consists of four decimal num bers separated by dots, e.g. 119922..1166..119999..11, representing the four bytes of the 32-bit address. The default action is to look up the associated host name. A host name or domain name consists of component names (labels) separated by dots, e.g. nniikkhheeffhh..nniikkhheeff..nnll The default action is to look up all of its Internet addresses. For single names without a trailing dot, the local domain is automatically tacked on the end. Thus a user in domain 991527 1 host(1) host(1) "nikhef.nl" can say "host nikhapo", and it will actually look up "nikhapo.nikhef.nl". In all other cases, the name is tried unchanged. Single names with trailing dot are considered top-level domain specifications, e.g. "nl." Note that the usual lookup convention for any name that does not end with a trailing dot is to try first with the local domain appended, and possibly other search domains. (As of BIND 4.9, names that have embedded dots but no trailing dot are first tried ``as is'' before appending search domains) This convention is not used by this pro gram. The actual suffix to tack on the end is usually the local domain as specified in the //eettcc//rreessoollvv..ccoonnff file, but this can be overridden. See below for a description of how to customize the host name lookup. AARRGGUUMMEENNTTSS The first argument is normally the host name (domain name) for which you want to look up the requested information. If the first argument is an Internet address, a query is done on the special "reverse mapping" domain to look up its associated host name. If the --ll option is given, the first argument is a domain zone name for which a complete listing is given. The pro gram enters a special zone listing mode which has several variants (see below). The second argument is optional. It allows you to specify a particular server to query. If you don't specify this argument, default servers are used, as defined by the //eettcc//rreessoollvv..ccoonnff file. EEXXTTEENNDDEEDD SSYYNNTTAAXX If the --xx option is given, it extends the syntax in the sense that multiple arguments are allowed on the command line. An optional explicit server must now be specified using the --XX option as it cannot be given as an ordinary argument any more. The --XX option implies --xx. The extended syntax allows no arguments at all, in which case the arguments will be read from standard input. This can be a pipe, redirection from a file, or an interactive terminal. Note that these arguments are the names to be queried, and not command options. Everything that appears after a '#' or ';' on an input line will be skipped. Mul tiple arguments per line are allowed. OOPPTTIIOONNSS There are a number of options that can be used before the specified arguments. Some of these options are meaningful only to the people who maintain the domain database zones. 991527 2 host(1) host(1) The first options are the regularly used ones. --vv causes printout to be in a "verbose" format. All resource record fields are printed. Without this option, the ttl and class fields are not shown. Also the contents of the "additional information" and "authority information" sections in the answer from the nameserver are printed, if present. Normally these sections are not shown. In addition, the ver bose option prints extra information about the various actions that are taken by the program. Note that --vvvv is "very verbose". This generates a lot of output. --tt _q_u_e_r_y_t_y_p_e allows you to specify a particular type of resource record information to be looked up. Supported types are listed below. The wildcard may be written as either AANNYY or **. Types may be given in upper or lower case. The default is type AA for regular lookups, and AA, NNSS, and PPTTRR for zone listings. --aa is equivalent to --tt AANNYY. Note that this gives you "anything available" (currently cached) and not "all defined data" if a non-authoritative server is queried. SSPPEECCIIAALL MMOODDEESS The following options put the program in a special mode. --ll _z_o_n_e generates the listing of an entire zone. E.g. the command hhoosstt --ll nniikkhheeff..nnll will give a listing of all hosts in the "nikhef.nl" zone. The --tt option is used to filter what informa tion is extracted, as you would expect. The default is address information from A records, supplemented with data from PTR and NS records. The command hhoosstt --ZZ --aa --ll nniikkhheeff..nnll will give a complete download of the zone data for "nikhef.nl", in the official master file format. --HH can be specified instead of the --ll option. It will print the count of the unique hostnames (names with an A record) encountered within the zone. It will not count pseudo names like "localhost", nor addresses associated with the zone name itself. Neither are counted the "glue records" that are necessary to define nameservers for the zone and its delegated zones. 991527 3 host(1) host(1) By default, this option will not print any resource records. Combined with the --SS option, it will give a complete statistics survey of the zone. The host count may be affected by duplicate hosts (see below). To compute the most realistic value, subtract the duplicate host count from the total host count. --GG implies --HH, but lists the names of gateway hosts. These are the hosts that have more than one address. Gateway hosts are not checked for duplicate addresses. --EE implies --HH, but lists the names of extrazone hosts. An extrazone host in zone "foo.bar" is of the form "host.xxx.foo.bar" where "xxx.foo.bar" is not defined as a delegated zone with an NS record. This may be intentional, but also may be an error. --DD implies --HH, but lists the names of duplicate hosts. These are hosts with only one address, which is known to have been defined also for another host with a dif ferent name, possibly even in a different zone. This may be intentional, but also may be an error. --CC can be specified instead of the --ll option. It causes the SOA records for the specified zone to be compared as found at each of the authoritative nameservers for the zone (as listed in the NS records). Nameserver recursion is turned off, and it will be checked whether the answers are really authoritative. If a server cannot provide an authoritative SOA record, a lame delegation of the zone to that server is reported. Discrepancies between the records are reported. Various sanity checks are performed. --AA enters a special address check mode. If the first argument is a host name, its addresses will be retrieved, and for each of the addresses it will be checked whether they map back to the given host. If the first argument is a dotted quad Internet address, its name will be retrieved, and it will be checked whether the given address is listed among the known addresses belonging to that host. If the --AA flag is specified along with any zone list ing option, a reverse lookup of the address in each encountered A record is performed, and it is checked whether it is registered and maps back to the name of the A record. This applies to forward zones. For 991527 4 host(1) host(1) reverse in-addr.arpa zones, it is checked whether the target in PTR records maps to a canonical host name. LLIISSTTIINNGG OOPPTTIIOONNSS The following options apply only to the special zone list ing modes. --LL _l_e_v_e_l Recursively generate zone listings up to this level deep. Level 1 traverses the parent zone and all of its delegated zones. Each additional level descends into another layer of delegated zones. --SS prints statistics about the various types of resource records found during zone listings, the number of var ious host classifications, the number of delegated zones, and some total statistics after recursive list ings. --pp causes only the primary nameserver of a zone to be contacted for zone transfers during zone listings. Normally, zone transfers are obtained from any one of the authoritative servers that responds. The primary nameserver is obtained from the SOA record of the zone. If a specific server is given on the command line, this option will query that server for the desired nameservers of the zone. This can be used for testing purposes in case the zone has not been regis tered yet. --PP _p_r_e_f_s_e_r_v_e_r gives priority for zone transfers to preferred servers residing in domains given by the comma-separated list _p_r_e_f_s_e_r_v_e_r. The more domain component labels match, the higher the priority. If this option is not pre sent, priority is given to servers within your own domain or parent domains. The order in which NS records are issued may be unfavorable if they are sub ject to BIND 4.9 round-robin reshuffling. --NN _s_k_i_p_z_o_n_e prohibits zone transfers for the zones given by the comma-separated list _s_k_i_p_z_o_n_e. This may be used during recursive zone listings when certain zones are known to contain bogus information which should be excluded from further processing. CCOOMMMMOONN OOPPTTIIOONNSS The following options can be used in both normal mode and domain listing mode. --dd turns on debugging. Nameserver transactions are shown in detail. Note that --dddd prints even more debugging output. 991527 5 host(1) host(1) --ff _f_i_l_e_n_a_m_e writes the resource record output to the given logfile as well as to standard output. --FF _f_i_l_e_n_a_m_e same as --ff, but exchange the role of stdout and log file. All stdout output (including verbose and debug printout) goes to the logfile, and stdout gets only the extra resource record output (so that it can be used in pipes). --II _c_h_a_r_s suppresses warning messages about illegal domain names containing invalid characters, by specifying such characters in the string _c_h_a_r_s. The underscore is a good candidate. --ii constructs a query for the "reverse mapping" iinn-- aaddddrr..aarrppaa domain in case a numeric (dotted quad) address was specified. Useful primarily for zone listing mode, since for numeric regular lookups such query is done anyway (but with -i you see the actual PTR resource record outcome). --nn constructs a query for the "reverse mapping" nnssaapp..iinntt domain in case an nsap address was specified. This can be used to look up the names associated with nsap addresses, or to list reverse nsap zones. An nsap address consists of an even number of hexadecimal dig its, with a maximum of 40, optionally separated by interspersed dots. An optional prefix "0x" is skipped. If this option is used, all reverse nsap.int names are by default printed in forward notation, only to improve readability. The --ZZ option forces the out put to be in the official zone file format. --qq be quiet and suppress various warning messages (the ones preceded by " !!! "). Serious error messages (preceded by " *** ") are never suppressed. --QQ selects quick mode, in which several potentially time consuming special checks are not carried out, and statistics gathering is skipped if not explicitly selected. --TT prints the time-to-live values during non-verbose out put. By default the ttl is shown only in verbose mode. --ZZ prints the selected resource record output in full zone file format, including trailing dot in domain names, plus ttl value and class name. 991527 6 host(1) host(1) OOTTHHEERR OOPPTTIIOONNSS The following options are used only in special circum stances. --cc _c_l_a_s_s allows you to specify a particular resource record class. Supported are IINN, IINNTTEERRNNEETT, CCSS, CCSSNNEETT, CCHH, CCHHAAOOSS, HHSS, HHEESSIIOODD, and the wildcard AANNYY or **. The default class is IINN. --ee excludes information about names that are not residing within the given zone during zone listings, such as some glue records. For regular queries, it suppresses the printing of the "additional information" and "authority information" sections in the answer from the nameserver. --mm is equivalent to --tt MMAAIILLBB, which filters any of types MMBB, MMRR, MMGG, or MMIINNFFOO. In addition, MMRR and MMGG records will be recursively expanded into MMBB records. --oo suppresses the resource record output to stdout. Can be used in combination with the --ff option to separate the resource record output from verbose and debug com ments and error messages. --rr causes nameserver recursion to be turned off in the request. This means that the contacted nameserver will return only data it has currently cached in its own database. It will not ask other servers to retrieve the information. Note that nameserver recur sion is always turned off when checking SOA records using the --CC option. Authoritative servers should have all relevant information available. --RR Normally querynames are assumed to be fully qualified and are tried as such, unless it is a single name, which is always tried (and only once) in the default domain. This option simulates the default BIND behav ior by qualifying any specified name by repeatedly adding search domains, with the exception that the search terminates immediately if the name exists but does not have the desired querytype. The default search domains are constructed from the default domain by repeatedly peeling off the first component, until a final domain with only one dot remains. --ss _s_e_c_o_n_d_s specifies a new nameserver timeout value. The program will wait for a nameserver reply in two attempts of this number of seconds. Normally it does 2 attempts of 5 seconds per nameserver address tried. The actual timeout algorithm is slightly more complicated, extending the timeout value dynamically depending on 991527 7 host(1) host(1) the number of tries and the number of nameserver addresses. --uu forces the use of virtual circuits (TCP) instead of datagrams (UDP) when issuing nameserver queries. This is slower, but potentially more reliable. Note that a virtual circuit is automatically chosen in case a query exceeds the maximum datagram packet size. Also if a datagram answer turns out to be truncated, the query is retried using virtual circuit. A zone trans fer is always done via a virtual circuit. --ww causes the program to retry forever if the response to a regular query times out. Normally it will time out after some 10 seconds per nameserver address tried. --VV prints just the version number of the hhoosstt program, and exits. SSPPEECCIIAALL OOPPTTIIOONNSS The following options are used only in special circum stances. --OO _s_r_c_a_d_d_r Define an explicit source IP address for sending name server queries. This may be necessary for multi-homed hosts with asymmetric routing policy. --jj _m_i_n_p_o_r_t --JJ _m_a_x_p_o_r_t Define a range of explicit port numbers to be assigned to the source IP address of the client socket for sending the nameserver queries and receiving the replies. Normally the kernel chooses a random free port number. This may be an inappropriate number if you are behind a firewall that filters random port numbers on incoming traffic. If only one of --jj or --JJ is given, a single explicit port number is defined. This is ok for UDP queries, but may not be sufficient for TCP queries. DDEEFFAAUULLTT OOPPTTIIOONNSS Default options and parameters can be preset in an envi ronment variable HHOOSSTT__DDEEFFAAUULLTTSS using the same syntax as on the command line. They will be evaluated before the com mand line arguments. QQUUEERRYYTTYYPPEESS The following querytypes (resource record types) are sup ported. Indicated within parentheses are the various kinds of data fields. AA Host address (dotted quad) NNSS Authoritative nameserver (domain name) 991527 8 host(1) host(1) MMDD Mail destination (domain name) MMFF Mail forwarder (domain name) CCNNAAMMEE Canonical name for an alias (domain name) SSOOAA Marks the start of a zone of authority (domain name of primary, domain name of hostmaster, serial, refresh, retry, expiration, default ttl) MMBB Mailbox domain name (domain name) MMGG Mail group member (domain name) MMRR Mail rename domain name (domain name) NNUULLLL Null resource record (no format or data) WWKKSS Well-known service description (dotted quad, protocol name, list of services) PPTTRR Domain name pointer (domain name) HHIINNFFOO Host information (CPU type string, OS type string) MMIINNFFOO Mailbox or mail list information (request domain name, error domain name) MMXX Mail exchanger (preference value, domain name) TTXXTT Descriptive text (one or more strings) UUIINNFFOO User information (string) UUIIDD User identification (number) GGIIDD Group identification (number) UUNNSSPPEECC Unspecified binary data (data) AANNYY Matches information of any type available. MMAAIILLBB Matches any of types MMBB, MMRR, MMGG, or MMIINNFFOO. MMAAIILLAA Matches any of types MMDD, or MMFF. The following types have been defined in RFC 1183, but are not yet in general use. They are recognized by this pro gram. RRPP Responsible person (domain name for MB, domain name for TXT) 991527 9 host(1) host(1) AAFFSSDDBB AFS database location (type, domain name) XX2255 X25 address (address string) IISSDDNN ISDN address (address string, optional subad dress string) RRTT Route through host (preference value, domain name) The following types have been defined in RFC 1348, but are not yet in general use. They are recognized by this pro gram. RFC 1348 has already been obsoleted by RFC 1637 and RFC 1706, which defines a new experimental usage of NSAP records. This program has now hooks to manipulate them. NNSSAAPP NSAP address (encoded address) NNSSAAPP--PPTTRR NSAP pointer (domain name) The following are new types as per RFC 1664 and RFC 1712. Note that the GPOS type has been withdrawn already, and has been superseded by the LOC type. PPXX X400 to RFC822 mapping (preference value, rfc822 domain, x400 domain) GGPPOOSS Geographical position (longitude string, lati tude string, altitude string) The following types have been reserved in RFC 1700, and are defined in RFC 2065 and revised per RFC 2035. SSIIGG Security signature KKEEYY Security key NNXXTT Next valid record The IP v6 address architecture and DNS extensions are defined in RFC 1884 and RFC 1886. AAAAAAAA IP v6 address (address spec with colons) The following type is documented in RFC 1876. LLOOCC Geographical location (latitude, longitude, altitude, precision) The following types have been proposed, but are still in draft. EEIIDD Endpoint identifier 991527 10 host(1) host(1) NNIIMMLLOOCC Nimrod locator AATTMMAA ATM address The following type is defined per RFC 2168. NNAAPPTTRR Naming authority URN The following type is proposed in RFC 2052, updated by RFC 2782. SSRRVV Internet service information The following type is proposed in RFC 2230. KKXX Key exchanger (preference value, domain name) The following type is defined in RFC 2538. CCEERRTT The following types have been proposed, but are still in draft. AA66 DDNNAAMMEE SSIINNKK The following type is defined in RFC 2671. OOPPTT EEXXAAMMPPLLEESS A very good summary and validation of an entire zone can be obtained with the following command: hhoosstt --GG --SS --CC --AA --LL 11 _z_o_n_e DDIIAAGGNNOOSSTTIICCSS FFAAIILLUURREE MMEESSSSAAGGEESS The following messages are printed to show the reason of failure for a particular query. The name of an explicit server, if specified, may be included. If a special class was requested, it is also shown. Nameserver [_s_e_r_v_e_r] not running The contacted server host does not have a nameserver running. Nameserver [_s_e_r_v_e_r] not responding The nameserver at the contacted server host did not 991527 11 host(1) host(1) give a reply within the specified time frame. Nameserver [_s_e_r_v_e_r] not reachable The network route to the intended server host is blocked. _n_a_m_e does not exist [at _s_e_r_v_e_r] (Authoritative answer) The queryname does definitely not exist at all. _n_a_m_e does not exist [at _s_e_r_v_e_r], try again The queryname does not exist, but the answer was not authoritative, so it is still undecided. _n_a_m_e has no _t_y_p_e record [at _s_e_r_v_e_r] (Authoritative answer) The queryname is valid, but the specified type does not exist. This status is here returned only in case authoritative. _n_a_m_e _t_y_p_e record currently not present [at _s_e_r_v_e_r] The specified type does not exist, but we don't know whether the queryname is valid or not. The answer was not authoritative. Perhaps recursion was off, and no data was cached locally. _n_a_m_e _t_y_p_e record not found [at _s_e_r_v_e_r], try again Some intermediate failure, e.g. timeout reaching a nameserver. _n_a_m_e _t_y_p_e record not found [at _s_e_r_v_e_r], server failure Some explicit nameserver failure to process the query, due to internal or forwarding errors. This may also be returned if the zone data has expired at a secondary server, of when the server is not authoritative for some class. _n_a_m_e _t_y_p_e record not found [at _s_e_r_v_e_r], no recovery Some irrecoverable format error, or server refusal. _n_a_m_e _t_y_p_e record query refused [by _s_e_r_v_e_r] The contacted nameserver explicitly refused to answer the query. Some nameservers are configured to refuse zone transfer requests that come from arbitrary clients. _n_a_m_e _t_y_p_e record not found [at _s_e_r_v_e_r] The exact reason for failure could not be determined. (This should not happen). _z_o_n_e has lame delegation to _s_e_r_v_e_r If we query a supposedly authoritative nameserver for the SOA record of a zone, the information should be available and the answer should be authoritative. If not, a lame delegation is flagged. This is also done if the server turns out not to exist at all. Ditto if 991527 12 host(1) host(1) we ask for a zone transfer and the server cannot pro vide it. No nameservers for _z_o_n_e found It was not possible to retrieve the name of any name server for the desired zone, in order to do a zone transfer. No addresses of nameservers for _z_o_n_e found We got some nameserver names, but it was not possible to retrieve addresses for any of them. No nameservers for _z_o_n_e responded When trying all nameservers in succession to do a zone transfer, none of them were able or willing to provide it. WWAARRNNIINNGG AANNDD EERRRROORR MMEESSSSAAGGEESS Miscellaneous warning messages may be generated. They are preceded by " !!! " and indicate some non-fatal condition, usually during the interpretation of the retrieved data. These messages can be suppressed with the -q command line option. Error messages are preceded by " *** " and indicate a serious problem, such as format errors in the answers to queries, but also major violations of the specifications. Those messages cannot be suppressed. _z_o_n_e has only one nameserver _s_e_r_v_e_r When retrieving the nameservers for a zone, it appears that only one single nameserver exists. This is against the recommendations. _z_o_n_e nameserver _s_e_r_v_e_r is not canonical (_r_e_a_l_s_e_r_v_e_r) When retrieving the nameservers for a zone, the name of the specified server appears not to be canonical. This may cause serious operational problems. The canonical name is given between parentheses. empty zone transfer for _z_o_n_e from _s_e_r_v_e_r The zone transfer from the specified server contained no data, perhaps only the SOA record. This could hap pen if we query the victim of a lame delegation which happens to have the SOA record in its cache. extraneous NS record for _n_a_m_e within _z_o_n_e from _s_e_r_v_e_r During a zone transfer, an NS record appears for a name which is not a delegated subzone of the current zone. extraneous SOA record for _n_a_m_e within _z_o_n_e from _s_e_r_v_e_r During a zone transfer, an SOA record appears for a name which is not the name of the current zone. 991527 13 host(1) host(1) extraneous glue record for _n_a_m_e within _z_o_n_e from _s_e_r_v_e_r During a zone transfer, a glue record is included for a name which is not part of the zone or its delegated subzones. This is done in some older versions of BIND. It is undesirable since unauthoritative, or even incorrect, information may be propagated. incomplete _t_y_p_e record for _n_a_m_e When decoding the resource record data from the answer to a query, not all required data fields were present. This is frequently the case for HINFO records of which only one of the two data field is encoded. _n_a_m_e has both NS and A records within _z_o_n_e from _s_e_r_v_e_r An A record has been defined for the delegated zone _n_a_m_e. This is signalled only during the transfer of the parent _z_o_n_e. It is not an error, but the overall hostcount may be wrong, since the A record is counted as a host in the parent zone. This A record is not included in the hostcount of the delegated zone. _n_a_m_e _t_y_p_e record has zero ttl Resource records with a zero ttl value are special. They are not cached after retrieval from an authorita tive nameserver. _n_a_m_e _t_y_p_e records have different ttl within _z_o_n_e from _s_e_r_v_e_r Resource records of the same name/type/class should have the same ttl value in zone listings. This is sometimes not the case, due to the independent defini tion of glue records or other information in the par ent zone, which is not kept in sync with the defini tion in the delegated zone. _n_a_m_e _t_y_p_e record has illegal name The name of an A or MX record contains invalid charac ters. Only alphanumeric characters and hyphen '-' are valid in components (labels) between dots. _n_a_m_e _t_y_p_e host _s_e_r_v_e_r has illegal name The name of an NS or MX target host contains invalid characters. Only alphanumeric characters and hyphen '-' are valid in components (labels) between dots. _n_a_m_e _t_y_p_e host _s_e_r_v_e_r does not exist The NS or MX target host _s_e_r_v_e_r does not exist at all. In case of NS, a lame delegation of _n_a_m_e to _s_e_r_v_e_r is flagged. It also applies to the PTR target host in reverse zones. _n_a_m_e _t_y_p_e host _s_e_r_v_e_r has no A record The NS or MX target host _s_e_r_v_e_r has no address. In case of NS, a lame delegation of _n_a_m_e to _s_e_r_v_e_r is 991527 14 host(1) host(1) flagged. It also applies to the PTR target host in reverse zones. _n_a_m_e _t_y_p_e host _s_e_r_v_e_r is not canonical The NS or MX target host _s_e_r_v_e_r is not a canonical name. This may cause serious operational problems during domain data retrieval, or electronic mail delivery. It also applies to the PTR target host in reverse zones. _n_a_m_e _t_y_p_e target _d_o_m_a_i_n does not exist The CNAME target _d_o_m_a_i_n does not exist at all. _n_a_m_e _t_y_p_e target _d_o_m_a_i_n has no ANY record The CNAME target _d_o_m_a_i_n does not seem to have any associated resource record, although the name seems to exist. _n_a_m_e address _A_._B_._C_._D is not registered The reverse lookup of the address of an A record failed in an authoritative fashion. It was not present in the corresponding in-addr.arpa zone. _n_a_m_e address _A_._B_._C_._D maps to _r_e_a_l_n_a_m_e The reverse lookup of the address of an A record suc ceeded, but it did not map back to the name of the A record. There may be A records with different names for the same address. In the reverse in-addr.arpa zone there is usually only one PTR to the ``official'' host name. _n_a_m_e address _A_._B_._C_._D maps to alias _a_l_i_a_s_n_a_m_e In case of multiple PTR records, the first one encoun tered points to the ``official'' host name. Subsequent ones are returned as alias names via gethostbyaddr() as of BIND 4.9. Note that PTR records are exempt from round-robin reshuffling. _z_o_n_e SOA record at _s_e_r_v_e_r is not authoritative When checking the SOA for a zone at one of its suppos edly authoritative nameservers, the SOA information turns out to be not authoritative. This could be determined by making a query without nameserver recur sion turned on. _z_o_n_e SOA primary _s_e_r_v_e_r is not advertised via NS The primary nameserver is not among the list of name servers retrieved via NS records for the zone. This is not an error per se, since only publicly accessible nameservers may be advertised, and others may be behind a firewall. _z_o_n_e SOA primary _s_e_r_v_e_r has illegal name The name of the primary nameserver contains invalid 991527 15 host(1) host(1) characters. _z_o_n_e SOA hostmaster _m_a_i_l_b_o_x has illegal mailbox The name of the hostmaster mailbox contains invalid characters. A common mistake is to use an RFC822 email address with a ``@'', whereas the at-sign should have been replaced with a dot. _z_o_n_e SOA serial has high bit set Although the serial number is an unsigned 32-bit value, overflow into the high bit can inadvertently occur by making inappropriate use of the dotted deci mal notation in the zone file. This may lead to syn chronization failures between primary and secondary servers. _z_o_n_e SOA retry exceeds refresh A failing refresh would be retried after it is time for the next refresh. _z_o_n_e SOA refresh+retry exceeds expire The retry after a failing refresh would be done after the data has already expired. _z_o_n_e SOA expire is less than 1 week The authoritative data at secondary servers expires after only one week of failing refresh attempts. This is probably a little too early under normal circum stances. _z_o_n_e SOA expire is more than 6 months Secondary servers will retry failing refresh attempts for a period of more than 6 months before their authoritative data expires. As BIND 8 concludes: war must have broken out. _s_e_r_v_e_r_1 and _s_e_r_v_e_r_2 have different primary for _z_o_n_e If the SOA record is different, the zone data is prob ably different as well. What you get depends on which server you happen to query. _s_e_r_v_e_r_1 and _s_e_r_v_e_r_2 have different hostmaster for _z_o_n_e If the SOA record is different, the zone data is prob ably different as well. What you get depends on which server you happen to query. _s_e_r_v_e_r_1 and _s_e_r_v_e_r_2 have different serial for _z_o_n_e This is usually not an error, but happens during the period after the primary server has updated its zone data, but before a secondary performed a refresh. Nev ertheless there could be an error if a mistake has been made in properly adapting the serial number. 991527 16 host(1) host(1) _s_e_r_v_e_r_1 and _s_e_r_v_e_r_2 have different refresh for _z_o_n_e If the SOA record is different, the zone data is prob ably different as well. What you get depends on which server you happen to query. _s_e_r_v_e_r_1 and _s_e_r_v_e_r_2 have different retry for _z_o_n_e If the SOA record is different, the zone data is prob ably different as well. What you get depends on which server you happen to query. _s_e_r_v_e_r_1 and _s_e_r_v_e_r_2 have different expire for _z_o_n_e If the SOA record is different, the zone data is prob ably different as well. What you get depends on which server you happen to query. _s_e_r_v_e_r_1 and _s_e_r_v_e_r_2 have different defttl for _z_o_n_e If the SOA record is different, the zone data is prob ably different as well. What you get depends on which server you happen to query. EEXXIITT SSTTAATTUUSS The program returns a zero exit status if the requested information could be retrieved successfully, or in case zone listings or SOA checks were performed without any serious error. Otherwise it returns a non-zero exit sta tus. EENNVVIIRROONNMMEENNTT CCUUSSTTOOMMIIZZIINNGG HHOOSSTT NNAAMMEE LLOOOOKKUUPP In general, if the name supplied by the user does not have any dots in it, a default domain is appended to the end. This domain is usually defined in the //eettcc//rreessoollvv..ccoonnff file. If not, it is derived by taking the local hostname and taking everything after its first dot. The user can override this, and specify a different default domain, by defining it in the environment variable _L_O_C_A_L_D_O_M_A_I_N. In addition, the user can supply his own single-word abbreviations for host names. They should be in a file consisting of one line per abbreviation. Each line con tains an abbreviation, white space, and then the fully qualified host name. The name of this file must be speci fied in the environment variable _H_O_S_T_A_L_I_A_S_E_S. SSPPEECCIIAALL CCOONNSSIIDDEERRAATTIIOONNSS The complete set of resource record information for a domain name is available from an authoritative nameserver only. Therefore, if you query another server with the "-a" option, only a subset of the data may be presented, since this option asks for any data that the latter server cur rently knows about, not all data that may possibly exist. Note that the "-v" option shows whether an answer is 991527 17 host(1) host(1) authoritative or not. When listing a zone with the "-l" option, information will be fetched from authoritative nameservers for that zone. This is implemented by doing a complete zone transfer and then filtering out the information that you have asked for. Note that direct contact with such nameservers must be possible for this option to work. This option should be used with caution. Servers may be configured to refuse zone transfers if they are flooded with requests. RREELLAATTEEDD DDOOCCUUMMEENNTTAATTIIOONN rfc819, Domain naming convention for internet applications rfc883, Domain names - implementation and specification rfc920, Domain requirements rfc952, DOD Internet host table specification rfc974, Mail routing and the domain system rfc1032, Domain administrators guide rfc1033, Domain administrators operations guide rfc1034, Domain names - concepts and facilities rfc1035, Domain names - implementation and specification rfc1101, DNS encoding of network names and other types rfc1122, Requirements for Internet hosts - comm. layers rfc1123, Requirements for Internet hosts - application rfc1183, New DNS RR definitions rfc1348, DNS NSAP RRs rfc1535, A security problem and proposed correction rfc1536, Common DNS implementation errors rfc1537, Common DNS data file configuration errors rfc1591, Domain Name System structure and delegation rfc1597, Address allocation for private internets rfc1627, Network 10 considered harmful rfc1637, DNS NSAP resource records rfc1664, Using DNS to distribute X.400 address mappings rfc1700, Assigned numbers rfc1706, DNS NSAP resource records rfc1712, DNS encoding of geographical location (GPOS) rfc1713, Tools for DNS debugging rfc1794, DNS support for load balancing rfc1876, Expressing location information in the DNS (LOC) rfc1884, IP v6 addressing architecture rfc1886, DNS extensions to support IP v6 (AAAA) rfc1912, Common DNS operational and configuration errors rfc1982, Serial number arithmetic rfc1995, Incremental zone transfer in DNS (IXFR) rfc1996, Prompt notification of zone changes rfc2010, Operational criteria for root nameservers rfc2052, Specification of location of services (SRV) rfc2065, DNS security extensions (KEY/SIG/NXT) rfc2136, Dynamic updates in the DNS rfc2137, Secure DNS dynamic update rfc2163, Using DNS to distribute global address mapping (PX) rfc2168, Resolution of Uniform Resource Identifiers 991527 18 host(1) host(1) (NAPTR) rfc2181, Clarifications to the DNS specification rfc2230, Key exchange delegation record for the DNS (KX) rfc2308, Negative cacheing of DNS queries rfc2317, Classless in-addr.arpa delegation rfc2535, DNS security extensions (KEY/SIG/NXT) rfc2538, Storing certificates in the DNS (CERT) rfc2541, DNS security operational considerations rfc2671, Extension mechanisms for DNS (OPT) rfc2782, Specifying the location of services (SRV) AAUUTTHHOORR This program is originally from Rutgers University. Rewritten by Eric Wassenaar, NIKHEF, <e07@nikhef.nl> SSEEEE AALLSSOO named(8), resolv.conf(5), resolver(3) 991527 19