3com Netbuilder w. Redhat router

In the beginning....3com Routers Netbuilder 2. 1 ethernet port, 1 rs232c
port.

I am trying to learn general routing, and would like to connect my 3com
Routers to LInux boxes running as Routers through Com ports, and extend my
network lab. However, with any box and any other router, I cannot get a link
light on the RS232 port of the 3com. I've tried with Windows and other 3com
routers using Null modem adapter, but no luck. I've tried using PPP over the
link, but the path will not come up.


Does anyone have experience using Linux routing over serial links, perhaps
with other vendor routers?

Thanks