How to make a mutli-homed host use one IP for a NAT'ed host

Greg Cope gregcope at
Thu Apr 21 17:12:06 CEST 2005

> Sorry, my mistake.  It was late at night after a long day.  :(

Many Thanks Grant.

No need to appologies - and your up already!

So I swapped to eth1 - and it would appear that packets are getting
marked as if I add in the ip route add command I can no longer connect
to an SMTP server from the mailserver (using telnet HOST 25)

So the last few hurdles...

I need to use the same router - an ADSL thing as everything else, I
just want the packets to be sent from a different $MAIL_INET_ALIAS IP
(as opposed to the usual INET_IP

$ ip rule add fwmark $SMTP_MARK table $IPROUTE2_SMTP_TABLE

Works fine and makes sense.

However I think these are the sticking points:

ip route add table $IPROUTE2_SMTP_TABLE dev $INET_IFACE src $MAIL_INET_ALIAS
ip route add table $IPROUTE2_SMTP_TABLE default via $INET_IP

I get 

$ ip route add table smtp.out dev eth0 src
$ ip route add table smtp.out default via
RTNETLINK answers: File exists

.241 is my internet gateway router, not the default external IP of my
firewall which is eth0= eth0:1= which is

Combinations of either of the above mean the mail server cannot
connect to an exteriror mail server.



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