root zone A queries

[Chris Thompson]

On Aug 17 2005, Pawel Rogocz wrote:
>> I have a number of BIND9 servers behind load balancer.
>> The load balancer does health checks by sending queries for "." of type A.
>> How soon, after a box looses its connection to the internet and no root
>> servers can be reached, will these queries start to fail ?
>
>I do not know what I was thinking , the answer is obvious:
>It depends on the value of max-ncache-ttl ( default 10800 secs )

Yes - capped at the value of SOA.minimum for the root zone (86400 secs).

I do wonder why this particular query is used as a "health check", though.
With nameserver software that didn't implement RFC2308-style negative
caching, it would go through to the real root servers. On the other hand,
maybe that's the intention.

-- 
Chris Thompson
Email: cet1 at cam.ac.uk