difference in responses between UDP and TCP

Anand Buddhdev anandb at ripe.net
Thu Jun 15 10:42:10 UTC 2017

On 15/06/2017 12:20, Arun Natarajan wrote:

> Hello,
> Wondering why we are seeing different serial numbers from a bind
> authoritative server for requests over UDP and TCP.
> dig +tcp soa @ns.example.com example.com +short
> ns1.example.com. hostmaster.example.com. 2017061505 10800 3600 3600000 3600
> dig +notcp soa @ns.example.com example.com +short
> ns1.example.com. hostmaster.example.com. 2017061506 10800 3600 3600000 3600

Perhaps the zone got updated between your queries.

Have you (as one should in a proper experiment) repeated these queries
to demonstrate that this is happening consistently?

If it is happening consistently, then it's possible that you have *two*
DNS servers listening on the server, one on the UDP socket, and another
on the TCP socket, and they're loaded with different zones.


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