Chris Pratt wrote:

I'm now setting up a bind server in which the third alias
is the address for incoming DNS queries. It appears
it's responding but even though the queries come in
on the third alias, they "go out" through the "primary"
address or more specifically, the packet count is
incremented in the Opkts total for the IP address first
attached to the interface via ifconfig (without an alias).
My problem appears to be that the packets really are
coming from the first IP as the source and are getting
blocked by my firewall as they should (the first address
is not supposed to be answering DNS queries).

Carefully not answering the 'why do these packets come from the
wrong address' question, but just pointing out that BIND is
actually rather more configurable in this respect than most
software.

You can control what IPs BIND will communicate on for various
purposes using the following statements in the options { } section
of named.conf:

   listen-on {
       127.0.0.1;
       12.34.56.78;
   };
   listen-on-v6 {
       ::1;
       1234:5678:9abc:def0::1;
   };
   query-source       address 12.34.56.78 port *;
   query-source-v6    address 1234:5678:9abc:def0::1 port *;
   transfer-source    12.34.56.78 port *;
   transfer-source-v6 1234:5678:9abc:def0::1 port *;
   notify-source      812.34.56.78 port *;
   notify-source-v6   1234:5678:9abc:def0::1 port *;

Note the 'port *' stuff -- due to the recent security problem with
the DNS protocol publicised by Dan Kaminsky, it is imperative that
the /source/ port on DNS traffic is allowed to be randomised.  See

http://www.kb.cert.org/vuls/id/800113 http://security.freebsd.org/advisories/FreeBSD-SA-08:06.bind.asc

and  make sure you install a patched version of BIND.

        Cheers,

        Matthew

--
Dr Matthew J Seaman MA, D.Phil.                   7 Priory Courtyard
                                                 Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey     Ramsgate
                                                 Kent, CT11 9PW

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