Clients keep sending DHCPDECLINE

Marc Perea marccp at
Fri Aug 20 13:57:21 UTC 2010

Hi Rasmus,
this problem can have a few different causes, but I remember having a similar issue when we had Vista attached to a Cisco relay agent on a router. After specific positioning of a packet capture to identify the behavior, Vista sends a gratuitous arp after the ACK as one final check to see if anyone else on the network has that IP before binding it to its interface for use. Unfortunately for us, our Cisco router was answering that arp with its own MAC, presumably identifying that the Cisco could get to that IP so it responded to the arp by proxy. We did a no ip proxy-arp on that interface and our router stopped responding to the g-arps, and things were quiet (and working).
Not sure if this is the case for you or not, but I'd at least get a sniff going just north of the client to see what situation is occurring that causes the client to DECLINE - delayed NAK perhaps from another piece of gear?
HTH -- Marc

>Over the last months I have suddenly seen a behaviour, that is new to
>2) Server DHCPOFFERs
>4) Server DHCPACKs
>6) Server abandons IP
>7) Goto 1, with new IP
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