Serving multiple subnets

Bruce Hudson Bruce.Hudson at Dal.Ca
Wed Sep 12 14:27:23 UTC 2007

> I am running a DHCP server in a particular segment.  On that segment, I
> need to serve a small DHCP pool.
> Connecting to this server are also relays (Cisco) in various other
> places.
> Each of these other places has a different pool of addresses assigned to
> them.
> So far, I have been unable to find a way to say "if you come from this
> relay, you are this group, if you come from that relay, you are that
> group" etc.

    Everything was easy up to this point but you have suddently switched
from talking about different pools to different groups. Perhaps you mean
the same thing but it is not entirely clear.

> When I look at the packets, I see there is a relay server ip address
> passed - is there a way to match based on that, or only on proper
> options?

    The DHCP server uses the relay address to determine what part of the
network, as described by the configuration file, a request came from; and
hence what addresses can properly be given out to satisfy that request.
This is extremely basic to how the server works. It happens without any
extra configuration required. If you have two subnets defined, each with
a pool of addresses, the server will assign an address from the correct
pool. Any options defined for the pool or the subnet will be assigned to
the client lease.

    Perhaps your requirements are more subtle than I read from your
message. It is possible to assign the client to a group based on the
relay address in the packet but very rarely would you need to.
Bruce A. Hudson				| Bruce.Hudson at Dal.CA
UCIS, Networks and Systems		|
Dalhousie University			|
Halifax, Nova Scotia, Canada		| (902) 494-3405

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