Simon Hobson dhcp1 at thehobsons.co.uk
Thu Mar 18 13:34:41 UTC 2010

kalyan Alle wrote:

>I was investigating a bug in dhcp 4.1.0 on my setup where the DHCP 
>client on the windows machine does not receive the DHCPNAK from the 

>I have set some start and end range of ipaddresses for the dhcp 
>client to get the ip address. After the client got the ipaddress 
>successfully i have changed the start and end range of ipaddresses 
>to some thing new. I did not receive any DHCPNAK after half of the 
>lease time is over since these pool or range of ip's are different 
>to the previous pool the ISC DHCP server should send DHCPNAK to the 

It's not a bug, it's documented (I think) operation.

Just because you've taken that address out of a range does not make 
the IP address itself invalid for the subnet - therefore the server 
will simply ignore the client and will NOT send a DHCP NAK. As long 
as the client asks to renew an IP address the server cannot hand out, 
the server will ignore it. There may well be another server handing 
out those addresses - which is valid.

The server will however send a DHCP NAK if the IP address is not 
valid for the network.

If you want the server to explicitly DHCP-NAK an address then you 
need to tell it to do so :

pool {
   range a.b.c.d a.b.c.e ;
   deny booting ;

Simon Hobson

WANTED: "Software CD ROM Kit" for Canon CLBP 360-PS printer (Canon 
part no RH6-3612, or possibly RH6-3810, or RH6-3610 might do). I've a 
dead HD and need this CD so I can replace the disk and re-install the 
printer OS on it.
This is NOT the same thing as the printer drivers to load on the 
computer - there's no problem there.
If anyone knows where I might get hold of one I'd be grateful - 
requests to Canon drew a blank, it's been out of support for years.
Alternatively, if anyone has one of these and would let me image 
their hard disk ...

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.

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