too much ARP traffic! help!

From: Michael (whoever_at_comcast.net)
Date: 12/11/03 

Date: Thu, 11 Dec 2003 17:26:11 -0500

Why does our Cisco 3620 router broadcast hundreds of ARP replies per day
that simply resolve its own hardware address to its own IP address?

I kid you not.

In each ARP packet, the target and sender MAC addresses are the same (the
router's)! Also, target and sender IP addresses are the same (yep, the
router's! )

How is this possible?

The router is connected to a Watchguard Firebox that is involved in NAT.