[H-GEN] How do I flush my dns cache ?

Greg Black gjb at gbch.net
Sat Aug 10 06:42:45 EDT 2002


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Robert Stanford wrote:

| I'm not talking about when I'm running a name server
| 
| If I contact a machine on dynamic dns and its IP changes at some stage,
| dns queres still use the old IP. I assume there is a dns cache somewhere
| in kernel space (im not running named) and I can flush it in /proc/ or
| by executing a command.

The original question was pretty vague.  This version does not
tell us much more.  I don't know what OS you're using, but no
Unix I'm familiar with caches DNS data in the kernel.  Routing
information (which is based on addresses, not names) is kept in
the kernel, but that's a different matter.

I expect that you have an /etc/resolv.conf file that points to
the actual name server that you use.  If it has cached stale
data, its operator needs to flush that cache to solve your
problem.

In reality, the source of the DNS data needs to be fixed so that
the TTL for dynamic data is short enough for cached data to time
out soon enough when addresses change.

If you were to tell us the name server you're using and the name
you're looking up and the answer you're getting and the answer
you expect, then we can diagnose this a bit more.  As it is,
it's just guesswork.

Greg

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