dhcp ( & cisco related ) question

Bruce Hudson Bruce.Hudson at Dal.Ca
Tue Aug 8 19:26:23 UTC 2006

> assuming I bring up several dot1q interfaces on the linux box, do I
> have to put an ip address from every subnet dhcp serves ? (dhcp server
> is not the same box as the gateway, is it possible to make it on a
> "broadcast" manner ?)

    DHCP normally works in a broadcast manner. What that means is that every
broadcast domain needs to see either the DHCP server directly or a relay
agent. A relay agent forwards packets to the server and forwards the replies
back to the clients. If your gateway will act as a relay, it can serve a
double role. Otherwise, you will need to give the DHCP server an address on
each subnet. The DHCP server needs the addresses so it knows how to map 
the VLANs to IP subnets.
> the dhcp relay feature of the cisco routers enables it as a relay host
> for dhcp messages from another server ?

    Correct, the "ip-helper-address" feature of a Cisco router causes it
to act as a DHCP relay, among other things. 
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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