Query regarding ARP request on a multi-homed system

[Chaitra Ramaiah]

Thanks guys for your reponses. It helped.

Taking a cue from your responses, did a bit of digging from resources
and this is what it all boils down to:
1) arp_filter works well if the IPs on the interfaces belong to
differrent subnets.
2) If the IPs share the same subnet, then arp_announce and arp_ignore
does the job. Specifically arp_ignore takes 1 and arp_ignore should
take 2 for this situation.

Thanks all.

Regards,
Chaitra


On Thu, Jun 26, 2014 at 11:28 PM, Dave Tian <dave.jing.tian at gmail.com> wrote:
> arp_filter may fit better.
>
> 	0 - (default) The kernel can respond to arp requests with addresses
> 	from other interfaces. This may seem wrong but it usually makes
> 	sense, because it increases the chance of successful communication.
> 	IP addresses are owned by the complete host on Linux, not by
> 	particular interfaces. Only for more complex setups like load-
> 	balancing, does this behaviour cause problems.
>
>
> -daveti
>
>
>
> On Jun 26, 2014, at 12:38 AM, wei zhang <asuka.com at 163.com> wrote:
>
>
> At 2014-06-26 02:13:30, "Chaitra Ramaiah" <linux.delve at gmail.com> wrote:
>>Hi,
>>
>>  Have a doubt regarding ARP behavior in case of a multi-homed linux box.
>>
>>  Assume there are two interfaces eth0 and eth1 each configured with
>>IPs belonging to differrent
>>  subnets. Say IP1 is assigned to eth0 and IP2 to eth1. Now if an ARP
>>request comes on eth0
>>  for IP2, what is the behavior on Linux?
>
> I'm not familiar with networking, but arp_announce and arp_ignore in
> Documentation/networking/ip-sysctl.txt maybe the answer!
>
>>
>>  Thanks in advance for your answers.
>>
>>Thanks,
>>Chaitra
>>
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