DHCP on VLANs

Whatever segment your DHCP server is servicing should be treated as a flat network, even though vlan's are present.

Make sure Vlan learning is turned on in the Switch's configuration program

The only issue is if you have remote workstations or devices on the other side of a wan link. DHCP becomes a little more troublesome, but I've solved this in the past
by making any of these static.

yes it is possible. i'm not a network guru but i know there are 2 ways to do what you're trying to do.

one is called iphelper or something and is a switch configuration that allows dhcp traffic to be used on multiple vlans.

the second way is not as good....it requires adding a nic for each vlan/subnet that you want dhcp on....

Ah say, if you're using a switch, how are you routing between VLANs? DO you have a L3 device in the switch? How will the clients even get to the DHCP server if the clients can't route to it?

I am assuming that somehow you ARE getting to the DHCP server, because you stated you are getting invalid addresses (assuming this is not the Win98 dummy address). But yes, DHCP servers can serve several different subnets. The addresses from a particular subnet are assigned using the source interface of the request, such as from a router.

So, when your client sends a DHCP request, the router picks it up and forwards it to the DHCP server from it's 'IP Helper' configuration. The DHCP receives the request, sees that the source is from your router's interface on your IP network and uses that source to give you the correct subnet network IP address. or something like that....actually i'm just guessing..

yes, you can support multiple vlans with a single dhcp server. if you're using a layer 3 device to route between vlans, you would use the router to turn the dhcp broadcast into a directed broadcast to the desired server. on a cisco network, you would use the ip helper address command to turn the broad casts into a directed broadcast or a unicast for the dhcp server. this command would allow you to use other broadcast intensive network applications too.

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