Date: Tue, 29 Jun 1999 18:10:10 -0600 From: Wes Peters <wes@softweyr.com> To: Kevin Bracey <kbracey@e-14.com> Cc: freebsd-net@FreeBSD.ORG Subject: Re: Old IP addresses hanging around in routes Message-ID: <37796062.63879A32@softweyr.com> References: <4cf1d91949%kbracey@kbracey.acorn.co.uk>
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Kevin Bracey wrote:
>
> In message <Pine.BSF.3.95.990629093117.11345C-100000@current1.whistle.com>
> Julian Elischer <julian@whistle.com> wrote:
>
> > you have a point and I admit that I can't remember exactly what I do in
> > this case. what about:
> >
> > ifconfig eh0 10.0.4.1
> > route add default 10.0.0.1
> > ifconfig eh0 down delete
> >
> > now what about the default route?
> >
>
> Still through 10.0.0.1, in the absence of any other information. If the
> interface comes back up, it will still be there. When we come to use the
> route with the interface down, we will find that we can't actually get to
> 10.0.0.1 so will have to back out. How this would be implemented is less
> clear.
>
> What did 4.3BSD do in this case?
4.2BSD retained a pointer in the routing table to an ifnet structure
that was no longer there. Ugh. I haven't looked at the 4.3 code, but
this problem gets really ugly in the face of the example given above.
You CANNOT keep the route, because the route has to refer to either an
interface or an address, and if the address or interface doesn't exist
anymore, the route cannot continue to exist.
The moral of the story is to use a routing daemon. The other moral of
the story is that routing daemons are evil, and difficult to configure
properly. ;^)
--
"Where am I, and what am I doing in this handbasket?"
Wes Peters Softweyr LLC
http://www.softweyr.com/~softweyr wes@softweyr.com
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