Re: Patch for route.c

H. Peter Anvin (
Tue, 8 Apr 1997 09:47:32 -0700 (PDT)

> This is _NOT_ nonsense! If you are running gated in the manner, you
> are contributing to LAN congestion by duplicating packets.
> >
> > And what if that single wire is a transit link? this ethernet is
> > joining two large networks, and there's a server on that ethernet?
> > then it needs routes for all the subnets in each network.
> >
> A machine on __any__ single __physical__ network link needs only two routes.
> Note the emphasis on "any" and "physical".
> (1) A route to its local network or subnet.
> (2) A route to all other places.
> If it's configured any differently, there will be duplicate packets on
> the same physical link. This does not mean that it won't work. It just
> means that it isn't working correctly.

I am sorry, but this is totally and utterly WRONG.

routed and gated do *NOT* perform routing!! All they ever do is
maintain routing *tables*. In fact, you can run either gated or
routed in a mode which prevents them from ever sending out
announcements, although that is the default if there is only one

A single physical network can have any number of gateways connected to
it. Hosts on that network need to know where to send their packets
that are going off the net. One way that can be handled is by relying
on ICMP REDIRECT, which is, in a sense, the simplest routing protocol
on the Internet. If so, the default route should be set to a host
(typically a router) which would know the proper route; in order to
avoid redirects in the common case you would typically pick the most
frequented router.

However, using routed or gated is perfectly legitimate, and will *not*
result in duplicate packets. If they are in announcing mode, you will
have unneccessary RIP packets, but as I said before, quiet mode is the
default for only one interface.