On Wed, 5 Apr 2000, Christopher W. Curtis wrote:
> Hello,
>
> I'm wondering if I've run across a routing bug or simply my own
> misunderstanding:
>
> eclipse:~# uname -a
> Linux eclipse 2.2.13 #1 Sat Nov 20 12:44:19 EST 1999 i586 unknown
> eclipse:~# route | grep default
> default styx.aet-usa.co 0.0.0.0 UG 1 0 0 eth0
> default aet-usa.com 0.0.0.0 UG 2 0 0 eth0
> eclipse:~# tracepath www.debian.org
> 1?: [LOCALHOST] pmtu 1500
> 1: 192.168.68.5 922ms !H
> Resume: pmtu 1500
> eclipse:~# route del default gw styx
> eclipse:~# route | grep default
> default aet-usa.com 0.0.0.0 UG 2 0 0 eth0
> eclipse:~# tracepath www.debian.org
> 1?: [LOCALHOST] pmtu 1500
> 1: 192.168.68.254 3ms
> 2?: 209.101.87.4
> 3?: 206.135.213.73 asymm 37
> [...]
>
> 'styx' is a computer with problems (or possibly another bug involving
> ipmasqadm and an NCR controller on the Alpha, still looking...) Either
> way, the machine went down, and Linux would not go to the default router
> with a metric of 2. I couldn't find any information regarding this in
> the HOWTOs, etc, but did not check the kernel source ...
>
> Thanks for any insight,
> Christopher
There is a specific networking list...
This is a common misunderstanding (also on configuring dedicated routing
hardware): A static route is a static route is a static route...
The routing statement just tells where to forward the packets with this
destination to. The routing of TCP/IP works completely distributed. Each
host only knows about the next hop and so the route taken between hosts
might even differ for packets going in the different directions. It has no
clue about what the destination does or does not with the packets.
So what you want to achieve can only be done by a routing protocol.
You need routed or gated or something newer for the more fancy protocols
running. It will explicitly exchange data with the other routers and then
set up the routing table according to which gateways it thinks to be
operational.
Static routes, however, are static. The fastest route is taken and that's
it. Maybe the kernel should simply reject any duplicate routes with the
same destination even with different metrics. If it doesn't, the IMHO only
sensible reason could be that it will distribute traffic to this
destination over the routes with the inverse ratio of the metrics.
> ipmasqadm and an NCR controller on the Alpha, still looking...) Either
> way, the machine went down, and Linux would not go to the default router
> with a metric of 2. I couldn't find any information regarding this in
The point is.. how do you think Linux would have learned about the other
machine going down? Plain TCP/IP has no means to achieve that. A routing
protocol might have guessed this after getting no response from a router
daemon on styx for a while.
Michael.
--
Michael Weller: [EMAIL PROTECTED], [EMAIL PROTECTED],
or even [EMAIL PROTECTED] If you encounter an eowmob account on
any machine in the net, it's very likely it's me.
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