Dave,
I dont know if you figured out how to do this as your post is a month old, but here goes...
To add multiple IP's on your SME just use ifconfig, at command line, and add IP aliases for each of the IP numbers you want it to use:
ifconfig eth1 alias xxx.xxx.xxx.171 netmask xxx.xxx.xxx.xxx
ifconfig eth1 alias xxx.xxx.xxx.172 netmask xxx.xxx.xxx.xxx
ifconfig eth1 alias xxx.xxx.xxx.173 netmask xxx.xxx.xxx.xxx
You get the drift as you need to run this for all your IP set. Clearly, you need to verfiy and use the correct netmask for this IP range.
Run "ifconfig eth1" to test and make sure the IP's were assigned right. Once tested you just need to install the approriate RPM's for port forwarding and packetfiltering from:
http://mirror.contribs.org/smeserver/contribs/dmay/mitel/contrib/This will install an interface in the server manager where you can setup the sme to foward the approriate ports to the right machines on the internal network. I haven't tested the port forwarding on a multiple public IP NIC but it should work the same.
cheers.
Joseph