Unsolicited DHCP NAK

Norman Elton normelton at gmail.com
Tue Jul 29 01:36:31 UTC 2008


I believe that unsolicited DHCP NAK messages should be dropped by
default. That is, if a client with a valid DHCP lease receives a DHCP
NAK, they should ignore it.

We're trying to identify a way to force a client to renew their IP
address after being moved from one virtual network (vlan) to another.
Right now, we "blink" their port, simulating them unplugging and
reconnecting to the network. This works great in 99% of the cases. If
a user is plugged into a mini-switch hanging off our network, then
they never actually see the link go down. It has been suggested that
we send a NAK packet, but my gut feeling says this would not be
supported in mainstream OSes.

I was going to reproduce this in the lab, but figured someone may be
able to reply quicker than I could craft a NAK packet.

Thanks!

Norman


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