Heartbeat with Broadvoice and wrt54g

I configured asterisk with the same config on two servers.
I installed the Heartbeat on both and configured.

My config looks like this:

  DSL router (WRTg54) port forwarding 5036, 10000-20000
   |                |

Asterisk1--------------Asterisk2

When one server goes down the second one takes over.

My problem:

When asterisk1 registers with broadvoice the router creates nat mapping to
the asterisk1.
Now, when asterisk1 goes down, asterisk2 cannot register with broadvoice
because the mapping still exists.
So, asterisk2 sends packets to register, but the packets comes back to
that mapping, which is useless.

Any ideas?

Bart

This is for you to read:

ultramonkey.org/3/topologies/ha-eg.html

also this:

linux-ha.org/HomePage