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added FAQ entry about root server A records not being returned

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as additional data
This commit is contained in:
Andreas Gustafsson
2001-07-19 22:11:10 +00:00
parent 3cb3f6867c
commit 21e0def4b2
1 changed files with 24 additions and 0 deletions
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FAQ
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@@ -163,3 +163,27 @@ user and set pid-file to "/var/run/named/named.pid", or set
pid-file to "named.pid", which will put the file in the directory
specified by the directory option (which, in this case, must be writable
by the named user).
Q: When I do a "dig . ns", many of the A records for the root
servers are missing. Why?
A: This is normal and harmless. It is a somewhat confusing side effect
of the way BIND 9 does RFC2181 trust ranking and of the efforts BIND 9
makes to avoid promoting glue into answers.
When BIND 9 first starts up and primes its cache, it receives the root
server addresses as additional data in an authoritative response from
a root server, and these records are eligible for inclusion as
additional data in responses. Subsequently it receives a subset of
the root server addresses as additional data in a non-authoritative
(referral) response from a root server. This causes the addresses to
now be considered non-authoritative (glue) data, which is not eligible
for inclusion in responses.
The server does have a complete set of root server addresses cached
at all times, it just may not include all of them as additional data,
depending on whether they were last received as answers or as glue.
You can always look up the addresses with explicit queries like
"dig a.root-servers.net A".