ps3cheats

I have used this site many times to either answer a question I didn't know or to affirm an answer I thought was correect.

I have a client who is currently using a Cisco Pix 506e conencted to a T1 data circuit. The T1 is handed off to me through an Adtran router provided by the ISP. My client recently had another data circuit installed which he wants to use as a failover should the primary T1 fail. This second data circuit is also handed off to me from the same ISP through an ISP supplied Adtran router. The problem I have is I need to see if there exists a firewall which will allow me to configure it for 2 data circuits. i know this can be done with a router such as the Cisco 2600 or 2800 series, but I since the data circuits are already going through separate Adtran routers before handed off to me, I wanted to just use a firewall.

ps3cheats

Yes, a router would actually handle it much better with many more options. I would recommend the 2811 model, but only if you take the Adtrans out of the picture.
You have options to load-balance/load-share/failover.
However, I would not consider a router as a firewall. yes, they can have firewall 'features', but they're still routers. Keep the PIX between the router and the LAN
Inbound NAT for internal servers (web) would be the most difficult to handle because you can't NAT 2 different public IP's to the same internal IP. Email is not such an issue because you can use MX records with priority settings.
If it was me, I'd still go with an ASA5510 firewall and keep the isp managed Adtrans. There is some advantage to having the ISP be responsible for everything down to the Ethernet hand-off to you. Since they are both from the same ISP, they can setup BGP to load-balance between them. Then you still only need a good firewall..