Why doesn't router remember IP/MAC?

One of my main desktops on my home network is Mandriva 2010.2 x86_64. I
have coded it with a static IP address of 192.168.1.107.

This morning, I was running Wireshark, and I noticed this exchange at
least twice every minute, ad infinitum.

23489 4030.195572 Cisco-Li_ea:bf:6a Micro-St_ab:cd:ef ARP Who has
192.168.1.107? Tell 192.168.1.1 60

23490 4030.195589 Micro-St_ab:cd:ef Cisco-Li_ea:bf:6a ARP 192.168.1.107
is at 6c:62:6d:ab:cd:ef 42

Why doesn't the router remember this? I would have thought he would
have got it once on startup, and then retained the information until
shutdown.

Thanks,
JimR

On 2011-10-27, JimR <(E-Mail Removed)> wrote:
> One of my main desktops on my home network is Mandriva 2010.2 x86_64. I
> have coded it with a static IP address of 192.168.1.107.
>
> This morning, I was running Wireshark, and I noticed this exchange at
> least twice every minute, ad infinitum.
>
> 23489 4030.195572 Cisco-Li_ea:bf:6a Micro-St_ab:cd:ef ARP Who has
> 192.168.1.107? Tell 192.168.1.1 60
>
> 23490 4030.195589 Micro-St_ab:cd:ef Cisco-Li_ea:bf:6a ARP 192.168.1.107
> is at 6c:62:6d:ab:cd:ef 42
>
> Why doesn't the router remember this?

It does -- for a 30 seconds, apparently.

> I would have thought he would have got it once on startup, and then
> retained the information until shutdown.

If that were the case, what would happen if you reconfugured the IP
addresses such that the MAC associated with a 192.168.1.107 changed?

You'd have to restart your router. People don't like having to do
that, so the router is designed to detect such changes by timing out
stale ARP cache entries after 30 seconds. The default ARP stale
timeout setting in the Linux stack is 60 seconds.

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