DHCP subnet

pat patkumar82 at gmail.com
Mon Apr 11 15:26:39 UTC 2011


Hi Simon

"If I read this right, you have a relay box of some sort, and you want to
somehow second guess the IP address the client is going to get - in advance
of the server allocating it ?"

Yes perfect, i need to do some sort of query to the dhcp server to get the
subnet configured that the server is ready to offer.

The reason for doing this is my box will be relay as well as a gateway to
the packet data network, where DHCP server A is placed in normal wireless
network and DHCP server 2 in the some sort of customized network such as
wifi, i wanted to put the check list in my box and map the client ip with my
database of Ip address, (worst case CLIENT X gets one Ip from DHCP A and
second IP from DHCP B for two different network access) .

without knowing the ip address range of the DHCP server A and B i can't
route with differential routing schemes

Is there a way to get the subnet information by query from dhcp relay server






some sort of Ip offloading to do that i need to have the DHCP server

On Mon, Apr 11, 2011 at 5:38 PM, Simon Hobson <dhcp1 at thehobsons.co.uk>wrote:

> pat wrote:
>
>  Is there a way to determine the scope/subnet information the dhcp server
>> would offer , actually iam working on some code so that if the client
>> address is from DHCP server A i will match in a intermediate box and route
>> the client traffic to destination via route A, and if the subnet offered
>> belongs to DHCP server B i will match in the intermediate box and route the
>> client to destination via route B. both the destination are same for client
>> but the path they choose will vary based on the ip address, i can't
>> predefine the route in the intermediate box i have to do mapping prior
>> routing can anyone help, the intermediate box could be dhcp relay also
>>
>
> If I read this right, you have a relay box of some sort, and you want to
> somehow second guess the IP address the client is going to get - in advance
> of the server allocating it ?
>
> Put simply, without complete visibility of the internal state of the server
> then it is not determinable in the general case. You would have to have a
> complete knowledge of the state of all leases/unused addresses to be able to
> take a good guess - and then it's not guaranteed.
>
> Perhaps if you could describe what you are trying to achieve then someone
> might be able to suggest something.
>
> --
> Simon Hobson
>
> 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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