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From: satz@cisco.com (Greg Satz)
Newsgroups: comp.dcom.sys.cisco
Subject: Re: Configuration problem
Message-ID: <31294@boulder.Colorado.EDU>
Date: 7 Jan 91 18:59:16 GMT
Sender: daemon@boulder.Colorado.EDU
Lines: 23

It is straight-forward to control what is advertised in outgoing RIP
updates. See the distribute-list configuration command. You can set it up
such that only default is ever advertised. 8.2 has the ability to perform
per interface filtering.

You have other problems besides getting the cisco router to advertise
routes with a source IP address of the secondary IP network. The hosts
sharing the same cable but on different subnets need explicit instruction
that they are on the same cable. Otherwise all packets will head off to the
router only to be issued back onto the same wire they were just received.
You can do this and can disable the resulting ICMP redirect if you so
choose.

Another option is to lie to those hosts on the secondary subnet. Tell them
they aren't subnetted at all. This will cause them to believe that all
hosts for your IP major network live on their same cable. Thus they will
ARP for everyone on that IP network. Hosts that share the wire will respond
and the router will answer (proxy) for all others. You do have to tell the
hosts on the primary subnet about the secondary (as the case above)
otherwise they won't know it's there when they want to start the
conversation.

Greg