nanog mailing list archives

Re: Intermittent incorrect DNS resolution?


From: Erik Levinson <erik.levinson () uberflip com>
Date: Wed, 16 Jan 2013 17:26:43 -0500

Good point.

While I haven't checked the distribution of source IPs yet, I briefly grepped for the User-Agent headers in the tcpdump output, and there's a higher than expected bot presence, particularly Baidu.

That said, there are also "normal" UAs (whatever that means, with every device/software pretending to be something else these days).

On 16/01/13 05:20 PM, RijilV wrote:
Also client programs don't always honor TTLs either.  For example, JAVA
defaults to ignoring TTLs and holding IPs forever.

*networkaddress.cache.ttl (default: -1)*
Indicates the caching policy for successful name lookups from the name
service. The value is specified as as integer to indicate the number of
seconds to cache the successful lookup. A value of -1 indicates "cache
forever".

Depending on who your clients are, your milage may vary.

.r'




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