More than one IP (sub)network on one ethernet cable


William C. VerSteeg (dcatla!dnwcv@gatech.edu)
11 Dec 87 22:13:59 GMT


I have bumped into a distressing situation dealing with getting a generic host
to communicate with other host with different IP network numbers on the same
network.

Let's assume that the following scenario for demonstration purposes.

Through the process of adding link-level (hardware) bridges, I have had the
unenviable situation of having more than one internet network appear on
what appears to be one ethernet cable. I want to telnet from my PC to a
SUN. They have different IP network numbers.

The PC will not generate a packet to this host in the absence of gateway
information.

The only way I can think of to make this work is to have the PC route to
a gateway, which sends an ICMP redirect back to the PC.

This leads me to my questions. What can be done to make the PC (or any other
device for that matter) directly access differring IP networks
that are directly connected to
its local ethernet? This situation runs against "normal" IP addressing
schemes. But does it violate any specific rules? Are there implementations
that handle this situation gracefully?

                                    Bill VerSteeg



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