DHCP Authorizing Subnets - dhcp-3.1.1

Simon Hobson dhcp1 at thehobsons.co.uk
Mon May 25 09:10:38 UTC 2009

<rohit.gupta3 at wipro.com> wrote:

>I have a doubt relating to the following scenario.
>DHCP Proxy own IP address must belong to one of that subnet...Now 
>DHCP Proxy is not allowing DHCP request to get Renew if it does not 
>fall under its own subnet. Is it possible to renew the DHCP 
>request.....even if it is not lying in the same subnet as of DHCP 
>Proxy itself ?

Can you elaborate a bit as to what you are trying to achieve/what 
isn't working ?

When a client is renewing an existing lease, it will normally use 
unicast packets directly to the server that issued the lease. You 
must have routing in place so that the packet can reach the server 
and the reply get back to the client.

As for the relay agent handling broadcast packets, I'm not aware that 
it checks the contents of the packet. It can't really do this as it 
doesn't have the knowledge of the network (and addressing rules) that 
the server does. So it's quite possible for a relay agent to support 
clients that have addresses in a different subnet on the same wire - 
but you MUST properly configure the server. If this is what youa re 
trying to do, then lookup "shared-network" in "man dhcpd.conf".

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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