DHCP lease renews every few seconds

[ether]

My logs are showing nearly constant DHCP lease renewal request from one host at a time. I will set a static IP for that host, but then another one starts. Initially I thought this was a client-side issue, but since it' s moving to different hosts I am now thinking it' s my Fortigate. Here' s what I am seeing in the logs:

10	2013-04-20	12:02:58	LAPTOP	 	Assigns IP address/configuration parameters to the client
 11	2013-04-20	12:02:58	LAPTOP	 	Client requests IP address/configuration parameters
 12	2013-04-20	12:02:44	LAPTOP	 	Assigns IP address/configuration parameters to the client
 13	2013-04-20	12:02:44	LAPTOP	 	Client requests IP address/configuration parameters
 14	2013-04-20	12:02:20	LAPTOP	 	Assigns IP address/configuration parameters to the client
 15	2013-04-20	12:02:20	LAPTOP	 	Client requests IP address/configuration parameters
 16	2013-04-20	12:02:06	LAPTOP	 	Assigns IP address/configuration parameters to the client
 17	2013-04-20	12:02:06	LAPTOP	 	Client requests IP address/configuration parameters

This is coming from a 224b running v4.0,build0521,120313 (MR3 Patch 6)

[Dave_Hall]

If this is happening on more than one computer, I would suspect a rouge DHCP server (or computer configured for ICS), faulty network switch or cable, or possible duplex/speed mismatch. I would also suspect the possibility that the DHCP lease pool may be exhausted. I would check the event history on those computer (with the issue) to see what it says about the network card. If there is a rouge DHCP server on the network, perform an ARP -a (on the computers affected) to see what mac addresses/IPs show up. Worst comes to worst get out your packet sniffer and/or run something like wireshark.