Multiple T1's and debian router/firewall

[William Sykes <wsykes@deepnines.com>]

All, 
do you all know of a Linux solution that would allow me to multihome my
office network for redundancy while maintaining www and mail presence?
Some type of router/firewall with multiple WAN links.


For example I have 2 t1's(from different ISP's) and if one goes down I
would like the other to Pass traffic.

Example 
Provider 1 gives me 1.1.1.0/24 where DNS and mail for my domain is
going.

Proveder 2 gives me 2.2.2.0/24

Provider 1 goes down.

Some type of Router/Firewall open source device at the perimeter of my
network identifies that the Provider1 link is failing and begins to
forward in and outbound traffic down Providers pipes.




Active/passive setup i guess?


Question:
If I have email and web services pointing to an ip on the Primary
network, if that network fails and the secondary network takes over via
some type of redundant Firewall/Device, how do I manage the DNS so that
the redundant network will now answer to www and mail requests? 

Im mainly confused about the DNS stipulations.


Multiple A records?
I dont know where to start.






Thanks
-In advance

-will

-will