caching question

Barry Margolin barmar at
Thu Oct 21 13:05:23 UTC 2004

In article <cl7va0$2p3b$1 at>, Pavel Urban <urbanp at> 

> Hello,
> as far as I know, when secondary nameserver asks primary if his zone is 
> up-to-date, it just checks for serial number. What about 
> non-authoritative (caching) nameserver?

Caching nameservers just use the TTL of the record.  When it runs out, 
it discards the cached data and queries an authoritative server.  The 
serial number is not supposed to be used.

> I have a customer that argued that our DNS server had wrong data for his 
> zone. It turned out that the customer forgot to increase serial number. 
> How BIND acts in this case?

If he forgot to increase the serial number, his change wouldn't have 
transferred to his slave.  If your caching server queries the slave when 
the TTL runs out, it will get the old data.

Barry Margolin, barmar at
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***

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