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2 DHCP servers on a network

We have 2 DHCP servers on our single domain. 2 different site locations connected by a VPN and of course 2 different subnets. 192.168.1.x and 192.168.2.x.

Am I right in thinking that we can only have 1 dhcp server running on a given subnet? ie the clients will find the only DHCP that should be visible on their own particular subnet?

If this is so, does this mean that there is no config required to point a client at a particular DHCP server?

The reason I ask is that I have just moved DHCP from a windows 2003 server to a 2008 DC and I want to make sure as much as I can that having activated and autorised the DHCP scope, the users will, when they start their computers in the morning, pick up the new DHCP service automatically?

Many thanks.

Cliff Galiher

You can have multiple DHCP servers on a given subnet. You cannot (without a lot of hoops) control which DHCP server a client will get an address from though. DHCP is broadcast based so it is a "first one to answer" type of situation. But for resiliency, it is not uncommon to see multiple DHCP servers on a subnet in larger deployments. Doing so does require some planning though, to make sure the same IP address isn't handed out by multiple servers and creating an IP conflict on the network. Some sort of cluster, shared database, or splitting a subnet so each DHCP server has a slice of the subnet for its own leasing purposes are all methods used in such deployments.

But to the second part of your question, no, you don't need to do anything special to "point" the client at a new DHCP server. It'll broadcast its intent to request (or renew) a lease and the new server will simply respond.

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Jordan Clark

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nigelbeatson

ASKER

Thankyou.

Am I right in thinking that a clients on subnet 182.168.1.x will not seek ip addresses from a dhcp server across a vpn on a disparate network ie 192.168.2.x?

I just want to be sure there will be no network chatter across the wan for a dhcp service.

Ie the dhcp server on 192.168.2.x will not broadcast it's service to clients on the 192.168.1.x network.

Many thanks

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