grc

Section: Domain Debug Tools Manual (1)
Updated: May 17 1993
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NAME

grc - check glue information  

SYNOPSIS

grc [ msglevel ]  

DESCRIPTION

Grc (glue records check) analyzes the glue records present in zone file. A glue record is an A RR specifying the address of a server that is an external host (a host not belonging to the zone). We can differentiate between two kinds of glue records:
a)
Necessary glue records

A RRs introducing the address of a server of a delegated domain and belonging to a delegated domain are necessary glue records. Note that the absence of these records can lead to problems, e.g. the unreachability of a zone.

b)
Unnecessary glue records
Otherwise, the glue record should not be present because its address is not under the authority of the zone. Furthermore this address can be retrieved from an appropriate server.

In order to help you to understand the concept of glue record, necessary and unnecessary (and missing) glue record, suppose that the ddt.pt zone has the following RRs:

ddt.pt.NSserver.eu.net.
ddt.pt.NSserver.ddt.pt.
server.ddt.pt.A192.1.1.1(1)
server.eu.net.A192.2.2.1(2)
grc.ddt.pt.NSserver.ddt.pt.
grc.ddt.pt.NSserver1.grc.ddt.pt.
grc.ddt.pt.NSserver2.grc.ddt.pt.
server1.grc.ddt.pt.A192.1.1.2(3)

In this case (1), (2) and (3) are, respectively:
(1) not a glue record
(2) unnecessary glue record
(3) necessary glue record

The address of server2.grc.ddt.pt should be present.

If msglevel is specified, only those messages belonging to level msglevel are displayed. Default is level 4.  

MESSAGES



Necessary glue record (name server of delegated domains)      (Comment)
If the glue record is needed, as stated in a). 
Unnecessary glue record (f present, should be removed)      (Comment)
If the glue record is not needed, you should remove it. Note that we can't guarantee that this record is in the master file, because if the server used for the transfer has an authoritative answer for that server's name, this information is also transfered with the zone. 
Missing glue record (the address of this host should be present)    (Warning 2)
If a necessary glue record, as stated in a), is not listed.
 

EXAMPLES

$ fc.up.pt | grc
 ### FC.UP.PT. ###
       Unnecessary glue records (if present, should be removed)
       obelix.fe.up.pt.          IN    A       192.82.214.19
       ciup1.ncc.up.pt.          IN    A       192.26.239.52

These records are not necessary because they are useless, case b). 

$ cat unl.pt | grc
 ### UNL.PT. ###
       Necessary glue records (name servers of delegated domains)
       host.fct.unl.pt.          IN    A       192.68.178.1
       tao.fct.unl.pt.           IN    A       192.68.178.17

These glue records are necessary as stated in a) above. 

$ cat pt | grc
 ### PT. ###
    Missing glue records (the addresses of these hosts should be present):
        muttley.ul.pt.
        dec4um.uminho.pt.
        decserver.det.ua.pt.
        zeus.ci.ua.pt.

Each of the mentioned hosts are name servers for sub-domains of pt. Thus, since they are under pt, their addresses should be listed in the pt zone file.  

SEE ALSO

ddt(1), named(8), RFC 1033, RFC 1034  

AUTHORS

Jorge Frazao <frazao@puug.pt>

Artur Romao <artur@dns.pt>

 

Index

NAME
SYNOPSIS
DESCRIPTION
MESSAGES
EXAMPLES
SEE ALSO
AUTHORS
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