two subnet''s?

Re: two subnet''s?

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>>>2. For some reason our secondary DNS server get's a lot of traffic. We
>>>don't want the backup subnet getting this traffic all the time.
>>
>>Your servers are <ns.retort.com> and <ns1.retort.com>. The root servers
>>appear to report them in alphabetical order, sorting numbers before
>>letters. I'm not sure if that's a feature of the root servers, or if
>>they've just been entered in that order. Since they're on the same subnet,
>>they're the same distance away from any name resolver, so the name resolver
>>chooses the first one it finds. That's why the secondary gets more traffic.
>
>For the record, another DNS guy I talked to doesn't think this is the
>case. He thinks it's just the UDP protocol. That is, if a UDP request
>fails on the first try it just drops it and gives up and goes on to send
>a request to the secondary name server.

Nevertheless, if you run nslookup or dig and query a root server for NS
records for <webfm.com>, the first listed is your secondary server,
<ns1.retort.com>. Remember that a resolver can't tell the difference
between primary and secondary.

BTW: If the first UDP datagram is really failing for a large proportion of
queries, you've probably got a network problem.

>This got me thinking. I can simply setup a single machine to handle both
>primary and secondary name servers via multihoming on one subnet, then
>specify the second machine acting as a third name server but configured
>as a primary server on the second subnet. Yes, confusing. The problem
>then is keeping the third name server synchronized but with a different
>class C. Client's would try to query the main name server _twice_ rather
>than once, then it would fall back on the third name server. The router
>on the second subnet would need to do NAT. Just thinking aloud...

QDNS won't use more than one interface per machine. Therefore, the
multihoming idea won't work. This is a feature that was requested several
months ago on the list, and I believe the official response was, "we'll
think about it".

Regarding keeping two different "primaries" in sync, you can automate it
with FileMaker and AppleScript. QuickDNS Pro Admin is highly scriptable.

>Anyone know the difference in the QuickDNS preferences between "minimum"
>and "time-to-live"? I'm told "minimum" is actually the TTL?

Minimum is short for "Minimum Time To Live", and is the default TTL used
for all records. The TTL field is actually the TTL for the SOA record, and,
if left blank, will default to the value of the Minimum field.
________________________________
Chris Buxton
Internet and Database Consultant

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