[Pdns-users] pdns-recursor local-address

[Marc Haber]

On Thu, Oct 25, 2012 at 10:52:44AM -0400, John Miller wrote:
> In the pdns manual (Chap. 17), I see a big warning:
> 
> "Warning: When binding to wildcard addresses, UNIX semantics mean
> that answers may not be sent from the address a query was received
> on. It is highly recommended to bind to explicit addresses."
> 
> Could someone point me to some docs for these "UNIX semantics?"  For
> some perspective, we're running an Apache server (with multiple
> IPs), listening on 0.0.0.0, that returns traffic from the IP it
> received its traffic on.

TCP, as a connection-based protocol, knows to use the right IP address
for its answers. UDP is not connection-based and thus does not do this
automatically. And PowerDNS needs to know its IP addresses to be able
to choose the correct one.

Greetings
Marc

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