[c-nsp] Does "backup interface" gratuitous ARP?

[Pete Lumbis]

This won't work, it won't let you put two IPs in the same subnet on the
router. What's a better solution would be an EEM script tied to an IP SLA
so when a failure is detected on g1/1 the EEM script shuts it down, removes
the IP, configures g1/1, and pings out, forcing an ARP.

As you mentioned BVI is a real solution. You need two physical interfaces
on a single logical segment, which sounds like a switching problem.

The only other option I can think of is putting G1/1 in a VRF and then
doing some sort of wacky route leaking between global and VRF.




On Wed, Aug 13, 2014 at 11:44 AM, Sam Stickland <sam at spacething.org> wrote:

> Hi,
>
> I'm exploring redundancy possibilities for a router hand off without a
> dynamic routing protocol. It's ugly and I'm not going to explain all the
> details here, but I basically have this configuration on a router:
>
> interface Gi1/1
>   backup interface Gi1/2
>   ip address 192.168.1.1 255.255.255.252
>
> interface Gi1/2
>   ip address 192.168.1.1 255.255.255.252
>
> If interface Gi1/1 goes down will the router send a gratuitous ARP when
> interface Gi1/2 comes up? I seem to remember that it's default IOS
> behaviour to always send a gratuitous ARP when an interface first comes up.
>
> I don't have test hardware to hand and I can't simulate this in GNS because
> ethernet interfaces are permanently up in dynamips.
>
> Regards,
>
> Sam
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