[ILUG] lynksys switches & network problem

[Kenn Humborg]

On Sun, Feb 11, 2001 at 10:31:05AM +0000, Kevin Gannon wrote:
> >I think that the problem lies at the switches because the
> >ping responses say that destination host unreachable.
...
> 3. The destination unreachable message is from your router/gateway saying it
>      doesnt know how to find the destination you are pinging. So you will 
> have to
>      look at the router/gateway. Without knowing what kind of 
> router/gatewat it is
>      I cant help much on that front.

Note that you can get "destination unreachable" messages from the localhost
as well.  If I ping a non-existent address on my local network:

[kenn at excalibur vax]$ ping 192.168.200.123
PING 192.168.200.123 (192.168.200.123) from 192.168.200.1 : 56(84) bytes of data.
 From excalibur.research.wombat.ie (192.168.200.1): Destination Host Unreachable
 From excalibur.research.wombat.ie (192.168.200.1): Destination Host Unreachable
 From excalibur.research.wombat.ie (192.168.200.1): Destination Host Unreachable
 From excalibur.research.wombat.ie (192.168.200.1): Destination Host Unreachable
 From excalibur.research.wombat.ie (192.168.200.1): Destination Host Unreachable
 From excalibur.research.wombat.ie (192.168.200.1): Destination Host Unreachable

This is the local IP stack saying "I've put out an ARP request and got no 
answer".  The gateway doesn't get involved because it's all on the same
subnet.

Deim, you should troubleshoot this by running tcpdump at various points in
the network.  (A Linux laptop is very handy for this.)  OTOH, the quick 
solution might be to just power-cycle all the switches...

Later,
Kenn