ARP Messages

Erik Norgaard norgaard at locolomo.org
Wed Feb 27 09:01:02 UTC 2008


Maechler Philippe wrote:
>>>  -------------                           
>>> |   server    |      switch      switch  
>>> |192.168.3.222|----[(3.x/24)]--[(3.x/24)]
>>> |80.242.192.80|bge1                |     
>>>   -------------                    |
>>>        |bge0                        -------------------
>>>        |                                               |
>>>     [switch]----[Gateway 80.242.192.65]---[INTERNET]   |
>>>        |                                               |
>>>        |                                               |
>>>     [switch]                                           |
>>>        |                                               |
>>>        |bge0                                           |
>>>  ---------------------------------                     |
>>> |  80.242.192.81 00:19:bb:25:7b:63|                    |
>>> | 192.168.3.226  00:19:bb:25:7b:64|--------------------
>>>  ---------------------------------
>> Do you see the same loop as I do?
>>
>> Request goes out on one interface, response comes back on the
> other - 
>> pretty much what the message says.
>>
> 
> Yes I see the loop, the error messages make sense but don't
> understand it :/ 
> I set up extra routes for the private network so how can a packet
> from the public interface arrive at a private one?
> 
> I'll recheck the cabeling, the routes on the servers and the
> switch the're connected to and give you feedback here

Well, it appears to me that you are on the wrong box to solve the 
problem. The server sends an error message as it should.

What happens is that your unnamed box receives an arp request on its 
bge0 interface, but sends the respond on its bge1 interface. You can use 
snort to listen for arp packets to see what's going on.

I do not know why you have created a loop, with correct routing and 
firewall there should be no need for a loop. The easy solution is to 
pull a cable - either one on that unnamed box.

Cheers, Erik


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