Greetings Alan,
: I have a mail server (and a test program as well) that binds to
: an address on eth1, and tries to connect to an address on eth0's
: network. Connections just time out. I've tested connections
: where I did not bind to a specific interface and I can make the
: connection.
:
: I've set ip_forward=1, and rp_filter=0 on all interfaces, and
: still cannot get a connection from eth1's address to something
: off of eth0's networks. Firewalls are disabled on the host.
Well....I don't think you should need to remove rp_filter unless you
are performing policy routing in addition to the simple routing
configuration you describe.
: Is there additional voodoo that needs to be set to allow traffic
: to cross from one interface to the other?
Did you pay your semi-annual chicken-sacrificing bill? If not, I
may not be able to help you.
OK, seriously, I have just tested exactly this sort of connection on
a similarly configured network. It works exactly as you want it to.
I'm guessing that you have some packet filter somewhere which is
interfering. How would you be able to tell? First, watch traffic
to see if it is ever leaving your router, and watch on your
mailserver to see that traffic is arriving:
router# tcpdump -nn -i eth0 host $MAILSERVER_IP
mailserver# tcpdump -nn -i eth0 host $ROUTER_IP_0 or host $ROUTER_IP_1
Now, make those connections from your router (with your TCP testing
tool of choice):
router# socat - TCP4:$MAILSERVER_IP:$SERVICE,bind=$eth0_IP
router# nc -vvs $eth1_IP $MAILSERVER_IP $SERVICE
If you don't see any traffic leaving your router, is it possible
that you have a strange POSTROUTING rule which does not refer to
output interface?
Good luck,
-Martin
--
Martin A. Brown
http://linux-ip.net/
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