TCP/IP and subnets

[jfh@CS.BROWN.EDU]

I am trying to configure the TCP/IP software on my 3670. Our campus has a 
backbone (128.148.0.0), which leads to a gateway (128.148.128.194), whose other
side is our local network (128.148.194.0). Picture:

128.148.0.0
================================|=================
				|
				| 128.148.128.194
			       [ ] Gateway
				| 128.148.194.1
	128.148.194.0		|
      --------------------------------------------------|
		  					|
		  			128.148.194.2	|
					Lisp Machine   [ ]
   
   Our namespace tells the 3670 that its IP address is 128.148.194.2, and
that the gateway is 128.148.194.1, and provides gateway service, and many
things work fine -- if we want to talk to someone at 10.0.0.51, it works. But
to talk to someone at 128.148.183.6, for example, we lose, because the 3670
thinks it's on network 128.148.0.0 (or so it says when we Peek at the
networks). It sends out the packet on its own interface, rather than through
the gateway, and nothing happens. The problem is that we are a class B subnet,
but the TCP/IP software seems to think we are not. Does anyone know a fix?
-John Hughes (jfh@cs.brown.edu)