Configure Cisco 3500 Catalyst Switch for Dual WANs

I currently have a Cisco 3500 switch that takes a single WAN connection from our firewall and switches it between our computers/phones as follows:

Cable Modem--->Firewall--->Cisco3500--->Computers

We will be getting a T1 line as well and I was wondering if we could connect both WANs directly to our switch using load balancing, send everything through the firewall, back to the switch and then out to the computers.  If so how would we configure the switch?  Thanks.

Cable Modem---||Cisco ||                    ||Cisco ||
T1-----------------||3500  ||---Firewall---||3500  ||------Computers
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The 3500 is an ethernet only switch, so you won't be able to directly connect the T1 line to this.  By load balancing over these two lines to the internet, you're going to introduce a lot of options that need to be considered.

May I ask why you're adding a T1 line?  What do you plan on terminating the line with?
The highest 3500s (3560, 3550XL too I think) can have layer 3 routing and can have SLB (load balancing).  However, it is very very basic and is for inbound connectivity so is not what you want.  Two options really, neither of them use the switch.

Depending on whether your T1s are to the Internet or cross site, and depeding on what firewall you have, you may be able to do something like two routes to the far end of the T1 with the same weight.  Generally this won't work though.

or aggregate the T1/Cable modems somehow using a device that sits between the switch and the links.  However, it looks like these are links to the Internet and I doubt that this will be possible.  What is just becoming available is bonded links to the Internet, which do aggregate for you  Either way there is no easy way to acheive this, and I don't see the switch helping.

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evotsiAuthor Commented:
Sorry, I should have made it more clear.  The T1 is terminated into another device that splits it between the phones and a data connection.  Basically I have two seperate internet connections.  I can't bond them because they are from different providers.  What I would like would be just some very basic round robin or even QOS type load balancing.
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