What do you have lame-ttl set to?
In message 361220.19486...@web121407.mail.ne1.yahoo.com, Fr34k writes:
Hello,
Given: BIND 9.7.2-P2 on Solaris 10.
For about an hour, I had a network event where a caching DNS server could not
get recursive queries back from authoritative DNS servers on the Internet.
Obviously, this is a problem.
Moreover, the authority for our most popular hostnames have set very low TTLs
(less than a minute), so nothing in cache for the server to call upon during
this hour long event.
Yuck.
A snoop of port 53 traffic at the time shows client PCs requested hostname
resolution -- as they would normally do.
Now, for the interesting part.
From the same snoop of traffic, the caching DNS server did not send ANY resp
onse
back to these PC clients for these low TTL popular hostnames.
Keep in mind that I did snoop until *after* the event started.
So, it may be the case that some BIND mechanism was behaving appropriate for
queries which it could not act upon. I can appreciate that BIND makes decisi
ons
with network performance in mind.
In my attempts to understand negative caching, Sections 7.1 and 7.2 of RFC 23
08
list Server Failure and Dead / Unreachable Server as (OPTIONAL) utilities.
Bind 9.7 ARM says that the server stores negative answers for (default) 3
hours; however, I'm not sure what the expected BIND behavior is.
Would some mechanism, such has max-ncache-ttl or clients-per-query, be
responsible for this lack of return traffic?
Anyone have ideas to share?
Thank you.
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Mark Andrews, ISC
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PHONE: +61 2 9871 4742 INTERNET: ma...@isc.org
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