DHCPNAK query

Simon Hobson dhcp1 at thehobsons.co.uk
Thu Mar 18 15:38:09 UTC 2010


kalyan Alle wrote:
>thanks for the reply simon. Can u point me to the location of the 
>documentation where it is given in the ISC dhcp package.

Good question !

man dhcpd.conf has :
DYNAMIC ADDRESS ALLOCATION
...

        If the server finds the address the client is requesting, and
        that address is available to the client, the server will send
        a  DHCPACK.   If  the  address is no longer available, or the
        client isn't permitted to have it, the  server  will  send  a
        DHCPNAK.   If  the server knows nothing about the address, it
        will remain silent, unless the address is incorrect  for  the
        network segment to which the client has been attached and the
        server is authoritative for that network  segment,  in  which
        case  the  server  will send a DHCPNAK even though it doesn't
        know about the address.

Now it's not terribly clear from that, but not being in a range 
statement would come under the category of "the server knows nothing 
about the address".

"the address is no longer available" would refer to a situation where 
the address is either leased to another client, or is in a range 
where access conditions (allow/deny) prohibit that client from being 
given the address.

To be honest, I only know about it because it's come up a few times 
in the mailing list, usually as part of a discussion on migrating 
clients from one server to another - for which one technique is in 
fact to run two servers and keep removing addresses from the 
available pools on the old server and adding them to the pools on the 
new server.

-- 
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 
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This is NOT the same thing as the printer drivers to load on the 
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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 ...

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