e-mail for Point-to-point T1

Unanswered Question
Jun 13th, 2007

We have a point-to-point T1 connection between two CISCO 2800 routers. One side has a static IP and the other has a Dynamic IP. The client wants their Server in the location that has a dynamic IP. So the problem is that we need mail to go to the exchange server but ip address at that location is dynamic. Can anyone give a sample cisco config on what statements you would need to have port 25 be forwarded accross the p-to-p T1 to the Server from the site that has a static IP address? Any help would be greatly appreciated.

I have this problem too.
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spremkumar Wed, 06/13/2007 - 20:22


Do revert back on how you are managing the point to point link when you have static on one side and dynamic ip on the other side ?

At least on the WAN interface you should be having static ip configured which you can make use of for the policy based routing for forwarding your mail traffic.

You can certainly make use of Policy Based Routing using ACL and matching the ports being used for mail communication and forward it to the next hop or set the next hop interface as the wan interface connecting the remote site...

If you still need info on the same do revert back...


Richard Burts Thu, 06/14/2007 - 05:57


I am also a bit curious how it works with one side having fixed IP and the other side having dynamic IP.

Would I be correct that what you want to do is to forward anything to the server IP address or do you really want to restrict it to mail. If you want to forward everything to the IP address there is a simple solution. If you want to restrict it to mail then you would need Policy Based Routing.

To forward everything to the server IP you would configure a simple static route specifying the outbound interface:

ip route serial 1/0 (or whatever the interface identifies is).

The good news here is that static routes pointing to outbound interface work well on point to point serial links (but they are problematic on LAN interfaces).

If you need PBR then you would set up the policy routing statements and in the route map you would set interface to the serial rather than setting next hop.



jhumiston10 Thu, 06/14/2007 - 09:43

It is a MPLS network between the two sites. The Server on the other end is a small business server so we would need ports 25, 80, 443, 444, 4125 to be forwarded over there as well. Would I use PBR for these ports as well?

Richard Burts Thu, 06/14/2007 - 10:24


If you want to forward those ports but not other traffic then you would use PBR and specify the ports that you want to be the basis of your forwarding decision. If you want to forward all traffic to the server address (without distinguishing various ports) then a static route should do without requiring PBR.

One thing to check: in your original post you refer to it as a point to point link. Is it a p-t-p serial link or is it some other kind of interface?




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