simple ping; pinging 101

[Lai Zit Seng]

THUFIR HAWAT wrote:
> On 7/6/05, Lai Zit Seng <lzs at pobox.com> wrote:
> 
>>How are you selecting to ping via eth0 or eth1? It seems to be that in
>>both cases your ping would have chosen eth0. Yet the 2nd case fails.
>>
>>Are you selectively pulling out physically the network cable to "select"
>>the network interface to use? This is not going to work!
> 
> ...
> 
> if you understand me and I understand you, then yes ;)
> 
> when the cable is plugged into eth0, and the network script on arrakis
> is restarted, then arrakis can ping caladan.
> 
> when the cable is plugged into eth1 and the same procedure is followed
> then the ping fails.  if the cable is then plugged into eth0 and the
> network script restarted then the ping succeeds again.
> 
> what's wrong with the "experiment"?  it seems to me that there's a
> problem with eth1.
> 
> the immediate goal is to ping from arrakis eth1 to caladan.

Nothing's wrong with the experiment. You just can't do it like this :) 
Ok, I'll cut short my reply since many others have followed-up.

It looks to me like you're trying to have "redundant" network 
connections for, perhaps, high-availability reasons. I.e. you still have 
network access should one link fail.

Also as others have mentioned, you'll need to bind the interfaces 
together, and needs similar support on the switch side. E.g. this is 
called EtherChannel in Cisco switches.

An alternative is to setup bridging on your systems. This is even better 
actually since now each system can connect to two separate switches, all 
hooked up in a redundant configuration, and running spanning tree 
protocol to eliminate forwarding loops. Then your IP interface itself 
will be on the bridge device.

Yes all these start to get more complicated :) But there should be 
HOW-TOs you can google for :)

Regards,

.lzs
--
http://zitseng.com/
> 
> 
> thanks,
> 
> Thufir
>