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Re: DHCP for multiple subnets (was: Re: Routing and bandwidth problem)



I didn't see the start of this thread, but here's my $0.02 ...

The DHCP server shouldn't care what interface the request came in on, rather
it looks at the source network of the request.

So you server could support many different ranges, provided there was suitable separation (i.e. a router) between the subnets and the server.

In your case, the server is acting as the router, but having separate interfaces on the server itself is not a requirement (of any DHCP server I know of)

Okay, it's been awhile since I set up our dhcp at work, but if I remember correctly, dhcp requests don't usually route. I believe that we had to set up our central router (a Cisco Catalyst 3550 set up to route instead of switch) to forward the dhcp requests to the dhcp server on our server subnet. Otherwise we'd have had to have had a dhcp server on each subnet.

Correct. DHCP is a broadcast. Routers don't normally forward broadcasts. Configuring the router (with "ip helper-address") causes it to send a unicast to the chosen DHCP server. Source address in the packet allows the server to respond with an address for the correct subnet.

Just wanted to point out that it's not necessary to have more than one NIC in the server to support multiple subnets. Of course, if the server is routing for those subnets then there's nothing wrong with that either.

Regards,
Matt.

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