Using multiple service providers through one OpenBSD box

I have a question similar to BariBari's.  I currently have both DSL and Cable Modem service.  I am using an OpenBSD v2.7 system with 3 interfaces as my gateway.  My network diagram looks something like this:

  DSL   C M
   |     |
   ---|---
      |
   OpenBSD
      |
      |
192.168.0.0/24

I am running servers in the 192.168.0.0 network that need to have public presence over the DSL circuit, but I want my workstations to NAT through the cable modem.  So far, I have been unsuccessful configuring the OBSD gateway to manage the traffic properly.  Listing both the DSL and cable modem default gateways in /etc/mygate (for the CM and DSL) causes OpenBSD to stop forwarding packets.

How can I shape my traffic to behave as I describe above?  Thanks!

i think the other guys advise is worth a try.

the two internal networks need there own nic.
then you can set the default rt for each network.
ex.
your cable ip 1.2.3.4
your dsl ip 1.2.3.5

your internal networks on two different nics.
192.168.1.0/24
192.168.2.0/24

say you want 192.168.1.0/24 hosts to be routed through the cable. 192.168.1.0 255.255.255.0 1.2.3.4
you want the 2.0/24 network routed by dsl
192.168.2.0/24 255.255.255.0 1.2.3.5

you might be able to use one nic. and alias it with both networks and still set the default rt but i think two nics will be cleaner, easier and safer seeing how you can filter at the MAC addy. for both networks and not just @ the header level.

if you have two internal networks because one contains servers like ftp, email etc.. which outside access is needed please use a dmz for those servers. you can still rt the dmz through the dsl and internal host through the cable. seeing how the cap. on u/l for cable is 128 and dsl is 385 and can go higher, i can see how folks running ftp and such would want to rt through the dsl.