Re: ARP handling in case of having multiple interfaces on same segment

["Christopher Friesen" <cfriesen@nortelnetworks.com>]

NIIBE Yutaka wrote:
> 
> Sometime, we have setting like following (say, in the migration
> process of changing IP networks, or perhaps wrong way of load
> balancing):
> 
>         +----------+
>         |eth0 eth1 |
>         +----------+
>            |   |
>     -------+---+------------
> 
> Current implementation of Linux doesn't handle this case.  The problem
> is ARP handling.  When ARP broadcast packet comes to the host, both
> interfaces receive the packet, and regardless of the device, we reply
> to that packet.  I think that we should not reply if the packet is not
> related to that interface.  If the ARP request is for eth1's address,
> we should not send reply from eth0.


Under later 2.2 kernels there is something called arp_filter that can be enabled
to give the exact behaviour you want. Apparently it is not yet in 2.4, but I
think that it should definately be added.

See the "ARP responses broken!" thread for more on this.

Chris


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