deny static ip

Chris Buxton chris.p.buxton at
Mon Sep 17 16:25:22 UTC 2012

On Sep 16, 2012, at 2:03 AM, Simon Hobson wrote:

> Alex Bligh wrote:
>>> It can ping, you have to set the option. For that to work, the offender
>>> must reply to pings
>> I wonder why it doesn't arping (issue arp 'who has?')
> It could do, but only on the wires local to the server. it would still need to use ping for networks reached via routers. Hence two lots of code.
> But, remember that this is a "last chance" check to pick up situations which are not supposed to happen. It's not required (AFAIK) by any RFC, and I don't think it's done by other servers.

I believe several other DHCP server packages offer this ping-before-assign behavior.

> If there is a clash, the client is supposed to detect that locally (?) and decline the lease offer.

And most clients do so, using some kind of ARP broadcast to make sure that the address is not already in use.

Chris Buxton
BlueCat Networks
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