ICMP Redirect mystery

Hi,

I just received a very unfriendly mail from the network supervisor of my
dorm accusing me of interfering with normal network operation.
Apparently he tried to ping some other pc on the network but instead got
a Redirect message from my private router that seems to bother him.

Accompanying the complaint he sent the following log:

> > ping wlan204
PING wlan204.x.y.net (192.168.1.202) 56(84) bytes of data.
- From pip38.x.y.net (192.168.2.38): icmp_seq=1 Redirect
Host(New nexthop: pip2.x.y.net (192.168.2.2))

192.168.2.38 is the ip of my small private SOHO single NAT router I use
to get all my devices online.
192.168.2.2 is the ip of the gateway my router uses to connect to the
internet.

Unfortunately I have absolutely no idea why my router even got the ping
at first place. Further on I have no idea why it then replied to it at all.
The network appears to be quite modern so I assume there are switches
instead of hubs so packets should only be directed to their actual
destination. Next I assume that one of the first rules for a router's
packet filter is to discard all packets, that are not addressed directly
to it.

At the moment I seriously doubt that my router alone is responsible for
the problem.

Any idea what there might be wrong and how to probably fix it?
For what its worth as a first measure I told my router not to reply to
any incoming pings at all.

Best regards
Rainer

Rainer Stolze wrote:
> Hi,
>
> I just received a very unfriendly mail from the network supervisor of
> my dorm accusing me of interfering with normal network operation.
> Apparently he tried to ping some other pc on the network but instead
> got
> a Redirect message from my private router that seems to bother him.
>
> Accompanying the complaint he sent the following log:
>
>>> ping wlan204
> PING wlan204.x.y.net (192.168.1.202) 56(84) bytes of data.
> - From pip38.x.y.net (192.168.2.38): icmp_seq=1 Redirect
> Host(New nexthop: pip2.x.y.net (192.168.2.2))
>
> 192.168.2.38 is the ip of my small private SOHO single NAT router I
> use
> to get all my devices online.
> 192.168.2.2 is the ip of the gateway my router uses to connect to the
> internet.
>
> Unfortunately I have absolutely no idea why my router even got the
> ping
> at first place. Further on I have no idea why it then replied to it
> at all. The network appears to be quite modern so I assume there are
> switches instead of hubs so packets should only be directed to their
> actual destination. Next I assume that one of the first rules for a
> router's packet filter is to discard all packets, that are not
> addressed directly to it.
>
> At the moment I seriously doubt that my router alone is responsible
> for the problem.
>
> Any idea what there might be wrong and how to probably fix it?
> For what its worth as a first measure I told my router not to reply to
> any incoming pings at all.
>
> Best regards
> Rainer

Not sure but it sounds like your router has RIP or RIP2 enabled. Turn it
off if you find it is on in your router.