named: IPsrc for ougoing UDP query != outgoing interface (weak-end model?)

[Barry Margolin]

In article <199912021337.IAA01587 at scramble.princeton.edu>,
Irwin Tillman  <irwin at Princeton.EDU> wrote:
>platform: BIND 8.2.2p5 on Solaris 2.6
>
>On a host with two physical interfaces attached to different networks,
>I see named sending UDP queries out via interface A, but with interface
>B's IPsrc address.
>Sort of a weak-end model behavior.
>
>(This is bad; when the packets reach the IP router, it drops them due to 
>IP spoof filtering.)
>
>Since I don't really need/want BIND to use interface B anyway, I tried to use
>the following option to force UDP queries to come from address A.A.A.A :
>
>   query-source address A.A.A.A port *
>
>However, that does not affect which physical interface is used for the
>outgoing packets;
>I still see the same behavior.

The OS chooses the outgoing interface based on what's in the routing table
entry for the destination it's sending to.  The source IP address has
nothing to do with it.

I suggest you set your default route to a gateway connected to interface A.

-- 
Barry Margolin, barmar at bbnplanet.com
GTE Internetworking, Powered by BBN, Burlington, MA
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