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

Christopher Friesen (cfriesen@nortelnetworks.com)
Thu, 19 Apr 2001 13:07:29 -0400


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

-- 
Chris Friesen                    | MailStop: 043/33/F10  
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