IP Route issue (dual inet connections)

Hello,

We have two internet connections. T1, ADSL. The ADSL should be used
for all incoming email and as a backup DNS. Everything works fine
looking down from 50k feet. We map two sets of public internal
addresses internal to multiple different machine inside the DMZ.
Works great. The problem is that when I pull the ethernet connection
from the T1 we will see an interupt in service on the ADSL. This
causes a problem. Logically, when the T1 is turned off (ether by
pulling the nic cable or complete poweroff) you would expect that the
ADSL line would continue to receive it's email. But this isn't the
case

I have equalized the lines and set a better priority for the ADSL and
still it doesn't work. I figured it could be an SNAT issue but I have
coded the links as well.

Any ideas? (55.55.55.x would be the ADSL line).

#!/bin/bash
ip route flush cache
ip rule add from 44.44.44.254/25 lookup 1
ip rule add from 55.55.55.254/29 lookup 2

ip route add 10.0.0.0/16 via 10.0.0.7 table 1
ip route add 10.0.0.0/16 via 10.0.0.7 table 2

ip route add 0/0 via 44.44.44.129 table 1
ip route add 0/0 via 55.55.55.249 table 2

ip route add default scope global equalize \
nexthop via 55.55.55.249 dev eth3 weight 1 \
nexthop via 44.44.44.129 dev eth0 weight 2

ip route add 44.44.44.254/25 via 44.44.44.129 dev eth0
ip route add 55.55.55.254/29 via 55.55.55.249 dev eth3


Thanks,

Gary Smith