[f-nsp] Redundant SI pair with virtual gateway ip

[Tom Banner]

Im currently running a single si450 using router code. It's Nating all the incoming traffic.

My servers use the private interface as the gateway IP. 

I'm looking to add a second SI for redundancy but not sure how the gateway situation with my servers would work. How do I setup a shared ip between the two SIs so that my servers can use it as a gateway?