How to setup 2 DHCP servers on 1 domain

[detroit]

How can I setup 2 DHCP servers in 1 domain?

This sounds simple, but all of our DHCP is restricted by MAC address, and we want to keep the reservations and all that the same.

I just want to put a 2nd DHCP server in another site for redundancy.

Anyone have a simple way to do this? Is there a way to "Replicate" the DHCP?

 

[wdoellefeld]

Only time I've ever seen redundancy using a second DHCP server is on a smaller network with no vlans. All it had was a different but compatable scope.

If your looking to back up a large amount of reservations, etc you could use DHCPEXIM and just refresh the backup every once in awhile.


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[detroit]

But I do want the redundancy. If my main server goes down, I have a backup DNS server, but would like to add a 2nd IP helper address into my routers, and then I could export and import the reservations, but not sure how this would work with issuing the leases.

 

[wdoellefeld]

How long are you setting leases for? Not enough time to recover from a loss of service?

Not sure about a second IP helper. Never heard of it but would be curious if that is possible.

You could, for lack of a better solution, have another server prepared up to take over DHCP and leave the service off. Then if disaster does happen add the IP of the down server as a second IP and turn up the service.




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[ADB100]

It is quite a common practise to have redundant DHCP servers. There are a few differnet stances on how to set this up but most people go with 2 DHCP Servers with non-overlapping scopes and the 80/20 split. This is where the primary server (usually the one logically closest to the clients) holds 80% of the available addresses and the 2nd server hold 20%. Your routers have 2 (or more) ip helpers configured for this.

http://download.microsoft.com/download/1/6/a/16a11c96-daa4-44a6-98ae-9f9ddb203b46/DHCP2003.doc

The DHCP service is cluster-able so a single scope can be used over a cluster to give redundancy.

Andy

 

[58sniper]

I'll second Andy's recommendations. The 80/20 method is a Microsoft Best Practices recommendation.

Pat Richard, MCSE(2) MCSA:Messaging, CNA(2)

 

[wdoellefeld]

I was under the impression you could only have 1 IP Helper. Looks like I'm wrong. Don't listen to me, I'm full of crap.

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