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From: jbvb@VAX.FTP.COM (James B. Van Bokkelen)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: IP routing and gateways
Message-ID: <9007130434.AA06815@vax.ftp.com>
Date: 13 Jul 90 04:34:39 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Reply-To: jbvb@vax.ftp.com
Organization: The Internet
Lines: 36

The Host Requirements RFC (lower layers, RFC 1122) has quite a bit to
say about this:

	1.) Is it the case that I need to provide a default gateway
	    address for IP packets that aren't destined for someone
	    within my subnet?

Yes.  Allowing several would be better than only one.

	2.) Do I need to implement an IGP like RIP and maintain routing
	    tables (even though this device only has one network
	    interface) so that I choose the correct gateway to route
	    my outgoing packets to, or is it OK to go to the same
	    gateway (default) every time?

It is quite acceptable to go to the first choice until you fail-over
to another in the default list based on upper-layer advice or failure
to reply to ARP, etc.  ICMP Redirect was designed to supplement the
default gateway with real-time advice about which gateway of all those
Oactive on the net at any given time is "best".  The intent was to allow
hosts to avoid hacking routing protocols...

	3.) If the answer to 2 is that it's not smart to go to the
	    same gateway every time, then is something like RIP (which
	    should be available on most Unix networks because of
	    routed) the way to go, or does the ICMP redirect take care
	    of letting me know that one internal gateway is better than
	    another for an outgoing packet?

The problem with implementing one routing protocol is that you'll
have to do them all (RIP, IGRP, OSPF, IS-IS....) before you have real
interoperability.  In particular, there are many people awaiting
their chance to be RIP's pallbearers (at least at their local sites).

James B. VanBokkelen		26 Princess St., Wakefield, MA  01880
FTP Software Inc.		voice: (617) 246-0900  fax: (617) 246-0901