Definity IP and NAT to IP Phones

[TheLaw]

We are looking to provide a solution for the following:

Remote Network is 10.1.1.1 w/20 Avaya IP Phones
Host network is running Definity G3-IP. The network is 172.1.1.1

The two networks do not wish to route each other's addresses so we are forced to employ either a NAT or PAT scenario. PAT is requested at this time since the folks on the 172. net would prefer to give up only one address, however, I don't believe PAT will work.

So, the question is, can an Avaya IP PBX support remote phones using 1-to-1 NAT or PAT? If so, would this be SIP based? H.323?

The network gear is mostly Cisco Gateways. A cisco g/w will be doing the NAT. I do have an "ip nat service sip" command that will allow the packet to be inspected and have the ip addr of the ip phone properly translated so the PBX registers the device w/the NAT'd address (this is how it works w/Cisco CallManager)

Now, assuming this can be done - are there any Avaya side server requirements? (such as SIP Proxy)

I am awaiting response from the Customer as to Avaya PBX and IP Phone versions, etc. The network diagram I have shows "Definity G3 IP"

Thanks!