exceedingly long time in assigning ip addresses

Simon Hobson dhcp1 at thehobsons.co.uk
Mon Dec 13 18:46:54 UTC 2010

Chris Buxton wrote:
>Since both DHCP servers are on the same LAN, could it be that the 
>other server has "authoritative" set? If so, is it possible to set 
>that server as "not authoritative"?
>The difference is whether the other server sends NAK responses to 
>requests. It could be that for the clients in question, the other 
>server's NAK is beating your server's ACK.

Turning off authoritative isn't a good idea if you can avoid it - it 
creates problems of it's own, such as clients moving between networks 
and not getting configured properly.

I have come across that before, it was a Windows XP client at 
customers site. We had arranged with the network guys to pipe their 
internal network across the campus so the receptionist in another 
building could be on their internal network - but when we plugged it 
in, it didn't work.

After much scratching of heads, and puzzlement as to why my Mac 
worked, I figured that their DHCP server wasn't authoritative and 
wasn't NACKing the clients requests for an invalid address. I think I 
picked an address, checked it wasn't in use, and configured the PC to 
use it - and then set it back to DHCP. The client then requested the 
address I'd picked and the server ACK'd it.

Better to configure both servers with the correct shared network - 
the ISC server will simply ignore requests for an address which is 
valid for the subnet but not available for lease.
Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
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