2 ISP with Inboud Mail Server

Unanswered Question
May 19th, 2009
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I've got an 1841 connected to 2 ISP, each ISP assigned me a /29. I want to use both connections for inbound SMTP connections to a mail server

Currently connections via ISP1 are working and are showing up correctly under show ip nat translations. But connections made to ISP2 doesn't seems to work unless I'm connection via a different IP in the /29 of ISP2.

I presume that traffic is being routed via the default route (ISP1) and not via the originating interface ISP2.

What configurations options must I enable to allow connections made via ISP2 is routed back via ISP2?



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rais Tue, 05/19/2009 - 11:33
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You can NAT the incoming source address on ISP2 link to a single address and add route to that address to ISP2 interface.


johanhanekom Wed, 05/20/2009 - 06:45
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Hi Rais

I've already added Natted the incomming source on both links:

ip nat inside source static tcp 25 64.30.xxx.xxx 25 extendable

ip nat inside source static tcp 25 64.36.xxx.xxx 25 extendable

But the problems seems to be that the outgoing traffic is routed via ISP1.

rais Wed, 05/20/2009 - 09:30
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Here you are NATing the inside client. You need to source-nat the incoming traffic from the Internet [ISP2 only] to your mail server.



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