IP alias/routing question

Matthew Seaman m.seaman at infracaninophile.co.uk
Fri Jul 25 17:13:10 UTC 2008

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

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 {;;
    listen-on-v6 {
    query-source       address port *;
    query-source-v6    address 1234:5678:9abc:def0::1 port *;
    transfer-source 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


and  make sure you install a patched version of BIND.



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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