routing and bridges


Paul Tsuchiya (tsuchiya@mitre-gateway.arpa)
Fri, 20 Mar 87 09:33:21 EST


Per you query about connecting two ethernet segments with different
IP network numbers with bridges which route on ethernet address....

It seems you have two problems.

First, getting your own IP-level gateways to know about the other net,
and second, getting other boxes in the world to know that both nets
are available through one interface. If you can solve the first
problem, then the second problem is easy because you can address both
nets via EGP (maybe I shouldn't assume EGP here, but I am guessing
that RIP et al. can also do this).

In solving the first problem, I would first ask whether the Bridges
pass on broadcast ethernet addresses. If they do, then ARP can be
used by the IP-level gateway to pass messages on to hosts irregardless
of the IP-network number. If not, then somehow the IP-gateway has
to have a local list of ethernet-address/IP-address tuples. Either
way, the problem is a local one, and shouldn't REQUIRE both ethernets
to have different network addresses (REQUIRE in the sense that the
IP routing architecture breaks if you don't have one address).

Also, if you want more that 254 hosts, to to a type B rather than a
type A address. Type B will give you 65534 addresses. Type A
network numbers are reserved for those REALLY BIG networks.

Paul F. Tsuchiya



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