>Well, in this case, the "router to the outside net" is an Ascend ISDN router, 
>so it is needed to connect to the outside (I don't have a way to make the NAT 
>box -- a NetBSD machine -- speak ISDN).  I was hoping that rather than setting 
>up two ether segments (one shared between the NAT box and the Ascend and one 
>shared between the NAT box and the inside machine(s)) I could put all the 
>machines on one segment (it saves a hub and a NIC).

Is that a Pipe 50/75?  If so the new firmware 5.0 is supposed to do NAT.

Good luck,
Paul