[asterisk-users] How to have failover sip interface?

[sean darcy]

My asterisk machine has 2 nic's. One nic (ETH0) is connected to a cable 
modem. The other nic (ETH1) is connected to an internal lan. The 
internal lan also has access to the internet.

The cable service, Time-Warner RoadRunner, is great when up, but is not
reliable. And sip connections are excellent. The connection through the 
internal lan (Verizon DSL) is reliable but lousy. Sigh.

When the cable is down, the interface connection to the cable modem
stays up. An ifconfig shows ETH0 as up. The only way to tell is to ping
an outside address.

I thought of bonding. But that won't work since it will see ETH0 as up,
even if the cable service is down.

Is there a way to implement network failover that actually checks for
true internet connection? This way I can keep my sip connection up, even 
if degraded.

sean