Pix multiple WAN Connections

I wondering if anyone has run into a situation such as this.

I have two WAN connections one is a Comcast Cable modem connection (currently being used with the PIX without issue) and a T1 that I have just had installed. Currently my email is routed over the comcast connection works great. What I would like to do is this. I have a failover PIX and would like to use both Pixs with both WAN connections. Both Pix's already have a second network card.

I would like my client traffic to over the Comcast circuit and the server based traffic over the T1. But I'd like to Pix to accept inbound SMTP from a secondary MX record on the comcast if the T1 is down. Also would like to failover to the circuit that is up if one is down. I don't believe I can do this with the PIX but I do have access to multiple Cisco routers.

Anyone have any ideas?
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You can't do it with the PIX. It simply does not have the advanced routing features that are required.
If you have a Cisco router, if you have the T1 module and two Ethernet ports, you might be able to get away with it.
Or, 2 cisco routers, one with 2 Ethernet ports connecting to the Cable modem and DMZ, and another with T1 module and one Ethernet port connecting to T1 and DMZ..

I must tell you that you have created quite a challenge for yourself.

The issue is default gateways. If you have two PIX's, one of them must be the default gateway of the email server. You can add a secondary default, but it won't do you any good unless the first PIX is completely unreachable on the LAN side. You're looking for resiliency on the WAN side of things..

The other issue is loss of connectivity. How will your Cable router notify everything else that it has lost connectivity? It is doubtful that an interface "down" condition will occur unless there is a total failure of the cable modem. There is no way for the router to know if the cable ISP is down upstream.

The T1, on the other hand, typically creates an interface event if the ciruit goes down. We can do lots of things to respond to interface events automatically.

OSPF can be your friend in this scenario. Both routers and both PIX's should be participating in OSPF areas. Area 0 on the "outside" between the routers and the PIX's, and Area 1 on the PIX inside interfaces. If your mail server is capable, it can also participate in OSPF and you can have dynamic routing all around...


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