[LARTC] Dual T1's and firewalls/Nat, Help?

[Jerry Amundson]

Hi.
I'm new to these tools, but well versed in Linux and networking, and I
just haven't found out some general stuff by going through the HOWTO's!

We have two (2) Internet T1's (different providers), each connected to
individual routers (one a Cisco, the other an Adtran, if it matters),
which are kept apart from the internal networks by two (2) Cisco PIX 
firewall devices. The latter do NAT/PAT, in addition to normal network
protection. One (1) firewall/T1 is currently "primary" as it is the 
Default Gateway for everything inside.

My *goal* is to put a Linux router in place as the Default Gateway to
be redundant and load balance across the T1's.

Q1: I'm in the right place, right? :-)

Q2: Assuming I am in the right place, the part I don't understand is
how to fit the Linux router in with the existing firewalls.

In a picture, we have:
----------------------
                            - DMZ1
ISP1 - R1 -ONet1-Firewall1-|
                            - INet1 <-> [internal NIC, Default Gateway]


ISP2 - R2 -ONet2-Firewall2-- DMZ2

And what we would like:
-----------------------
                            - DMZ1
ISP1 - R1 -ONet1-Firewall1-|
                            - INet1 -|              |
                                     | Linux Router | <-> [new Gateway]
ISP2 - R2 -ONet2-Firewall2-- DMZ2 ---|              |

I can revisit the HOWTO's, and many fine sites referenced in this list,
but I wanted to make sure I was on the right track...

Please be gentle - I don't even know what the abbreviations tc, htb, or
imq mean, yet!!

Thanks,
jerry