Re: kernel not processing ICMP Redirects

The Cow of Destruction (
Sat, 2 Nov 1996 11:42:50 -0600 (CST)

On Fri, 1 Nov 1996, Alan Cox wrote:

> > My linux box (actually several of them) which are running 2.0.22 &
> > 2.0.23 (redhat 3.0.3) are not processing ICMP redirects from my cisco
> > 2501. I get the message in the kernel log (syslog) "ICMP redirect
> > from" but the routing table is not updated properly. Is
> > the kernel supposed to do this (I thought it did back in 1.2.13 days).
> > If the kernel is not supposed to be doing this how do I go about
> > updating the route table?
> With a routing daemon ?
> If your kernel is built with CONFIG_IP_FORWARD (ie its a router) then it
> ignores ICMP redirect. See the router requirements RFC's. If its got
> it disabled its a host so it honours them.
> Alan

If he has CONFIG_IP_FORWARD, the message he should be seeing would be
something along the lines of "icmp: ICMP redirect ignored." with some info
on the packet following... Otherwise, his host should be honoring the
redirects (unless theyre trying to redirect him somewhere thats not on the
same subnet, or other illegal redirects)

BTW has someone already tested all of these ICMP features, and shown that
they work?