ICMP redirect from <gateway> in /var/log/messages?

ICMP redirect from <gateway> in /var/log/messages?

Post by Stian Seeber » Wed, 30 Jul 1997 04:00:00



Hi,

Having a problem with a couple of linux boxes I'm setting up at work...

On one I have networking set up just fine, except for those (thousands of)
ICMP redirect messages in /var/log/messages. That to me says something is
not as it should!

On the other box (diffrent networking card but otherwise just about
identical) I get the same messages, but it seems like the routing goes to
h*ll as soon as I start woring on the network. Ping etc. work just fine,
but if I attempt to cat a file that is larger than about 2k on a remote
host after telneting to it, the window seems to hang, and it is impossible
to get routing information. It looks like this:


Kernel IP routing table
Destination    Gateway       Genmask       Flags Metric Ref    Use Iface

And that's all she wrote :-/ If I run /etc/rc.d/init.d/network stop then
start the system comes back online.

My thinking is that I either haven't set the networking up correctly on
the boxes or that I'm missing something in the kernel. If anyone has any
idea of what the h*ll is going on I'd appreciate an email...my boss is
starting to look at me with that 'I thought you knew what you were doing'
look ;-)

Thanks!

Oh btw: were running RedHat linux 4.0 with kernel 2.0.18...haven't had
time to get the 4.2 CD just yet :-/

 
 
 

ICMP redirect from <gateway> in /var/log/messages?

Post by Bob Hau » Thu, 31 Jul 1997 04:00:00




Quote:> On one I have networking set up just fine, except for those (thousands of)
> ICMP redirect messages in /var/log/messages. That to me says something is
> not as it should!

Routing is broken (well, "sub-optimal" at least).  Some router on the
network is trying to tell you that there is a better route to the
destination than the one you are using.  Probably you need to be running
routed or adding some additional static routes to your setup.  What does
your network topology look like?  Here's an example of a situation where
you'll get redirects:

NET-1<-------->ROUTER-1<----YOU---->ROUTER-2<------------->NET-2
                 |
                 +--->NET-3

If you have a default route to ROUTER-2 and nothing else, and you send
packet that is for NET-1 or NET-3, you'll get an ICMP redirect because
ROUTER-1 is a better choice.  The fix is to add network routes for all the
reachable networks or use a routing protocol like RIP to do this
automatically.

If you have more than one gateway on your LAN segment, you'll probably run
into this sooner or later.

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