DHCP Server - Replica for redundancy

[Eudora931]

Hi,

 

I was wondering how easy it would be to set up say a spare laptop as a replica DHCP server in case our DC were to fail...?

 

Thinking behind this being that if DC were to go down, I would still need wireless AP's to get an IP address so that we could continue out to the internet?..

 

Is this possible? would it work?

[Roberto]

Why a laptop? You can set any other server up as a DHCP server, and have it up and running alongside the current "live" one. Some notes here on that.

[Boredguy]

If you have Windows 2012 you can setup DHCP failover for just this eventuality.

Windows 2008 had the feature where your DHCP server could be load balanced over a couple of servers but not sure if it had the failover as well.

[Eudora931]

Just someone mentioned that it was easy to do and could run on a laptop in the corner .... We only have one server which does DHCP ,DNS , AD etc...

 

So thought I'd ask the experts on here to see if it was just a throwaway comment or something I can actually do...

[Roberto]

Just someone mentioned that it was easy to do and could run on a laptop in the corner .... We only have one server which does DHCP ,DNS , AD etc...

 

So thought I'd ask the experts on here to see if it was just a throwaway comment or something I can actually do...

 

It could go on a laptop in the corner, but in that case what would the laptop run? It would really need to run windows server (in which case, why not a desktop built up a bit to act as a second server for DNS and AD too, running all the time?) or Linux with DHCP configured, rather than windows desktop.

[3s-gtech]

The laptop/PC/extra server will need to run Server 2012 or later (as you have a Windows DHCP server) as well as your existing server. That's when proper DHCP failover support came in (rather than split range). It's very easy to set up once in place.

[Eudora931]

Thanks for the replies - much appreciated. Our current server is server 2088 R2 Standard running CC4 ...

Looking to upgrade to Server 2012 with changeover most likely to be summer ..

[Roberto]

Thanks for the replies - much appreciated. Our current server is server 2088 R2 Standard running CC4 ...

Looking to upgrade to Server 2012 with changeover most likely to be summer ..

 

It should work with 2008r2 on the "second server", and Windows will certainly allow you to mix and match domain controllers so having a new 2012r2 server alongside the 'old' 2008r2 server wouldn't be an issue for either DC services, DNS or DHCP. You'd need to effectively set up an 80/20 split and manually failover between the two DHCP servers until you'd upgraded both to 2012 or newer for DHCP resillience however.

 

You'd want to speak to RM (or wait to see if someone who knows CC4 better than I can advise) to ensure you can stand up a none-CC4 DC in a CC4 network. I seem to recall previous versions of CC used to get in the pouts a bit if you tried this.

Edited March 2, 2016 by Roberto

[Duke5A]

If you needed to be cheap about it you could always split the scope across two servers. Way, way back in the day I setup a network with two DHCP servers: one Win2k Server and the other Linux running DHCPD. Figure the correct size of the subnet you need for the network and double it. Add IP Helper to the VLAN pointing to both servers and have one server hand out addresses for the first half of the subnet and the second server hand out the ladder. If one server goes down the second will simply respond and there is no possibility of an address conflict since they're no handing out the same addresses.