Secondary DNS/DHCP using server 2008 r2 and server 2012 r2

I am managing two separate locations, both have a single 2008 R2 DNS/DHCP server and they both hold the FSMO roles. I want to create a secondary DNS/DHCP server at each location for redundancy. Here is where my problem lies, I have 2 servers running server 2012 R2 to use as the secondary. I have had no issues setting up redundant DNS with the 2008 and 2012 boxes. I've hit a roadblock with DHCP and i'm not liking what Google has to say.

Ideally i'd like to run a DHCP hot standby with the 2012 box. Load balance is an option as well if needed. One site would have no issues running a split scope as i only have ~60 devices. The other location has almost 200 devices, a split scope would be difficult to pull off.

I cannot upgrade the 2008 r2 boxes but i can downgrade the 2012 r2 boxes to 2008 r2.

Any thoughts or ideas would be appreciated.


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Paul MacDonaldDirector, Information SystemsCommented:
If I understand you correctly, you have two sites, each with a single domain controller, which provides DNS and DHCP.  You want to provide redundancy for DNS and DHCP.

First off, I'd advocate for adding a second domain controller at each site.  DNS and DHCP will do you no good if you can't log in to the network.  The second domain controller should also serve DNS, so that's two birds with one stone.

I'm unsure about your concerns regarding a split zone for your 200-seat site, and you don't go into details.  I presume you have a network using a straight class C address space, and think splitting the zone won't cover all seats if one server goes down.  You'd be right about that, but having half your people working is better than having none of your people working.  In any case (and presuming I'm right about your concern) you can always change the subnet mask on your network to give yourself a larger address space and therefore more than enough addresses for DHCP to hand out should one DHCP server be unavailable.
I have 2 servers running server 2012 R2 to use as the secondary

ideally setup dhcp to lease out IPs across locations is not recommended as this states that only dhcp should get failed and both site remains online, this could not be the case

What you can do, you have two 2012 R2 servers at location 2, build DHCP software cluster at location 2 which can do load balancing and / or failover as well.
It can lease out IPs to 2nd site as well but until link between two is online, if link goes offline...
hence with location1 as well install 2 * 2012 r2 servers and built dhcp failover cluster

Software DHCP failover cluster is 2012 feature
If 2012 is not an option, then you need to setup dhcp failover cluster on 2008 r2 which will support only failover and not load balancing
StinkyPete1Author Commented:
Paul, Sorry for the vague description i just wanted to get the issue out there and get some feedback. I have 2 dc at each location and when i set up the secondary 2012 box with dns i made that a dc as well so i'm covered on that end. I am running a straight class c address scheme, and you nit the nail on the head with that. Even if i do a 50/50 split half the users won't get a lease. although as you state, that's better then nothing. I will be replacing the current 2008 FSMO servers in 18 months or so at which point i will change the subnet.

I was really hoping i could get server 2012 and 2008 to play nice for this but from what I've seen they will for DNS but not for DHCP.

So it looks like my only real option is to downgrade the 2012 box to 2008 and either do split scope or cluster.
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StinkyPete1Author Commented:
Mahesh,  I can't go with 2 2012 servers at this point, i'm locked into the current 2008 FSMO servers for the time being.
Paul MacDonaldDirector, Information SystemsCommented:
"I was really hoping i could get server 2012 and 2008 to play nice for this but from what I've seen they will for DNS but not for DHCP."
How are 2008 and 2012 not "playing nice"?

Note you can create a DHCP scope on each server, each with half the available IP addresses.  The two scopes don't need to know about each other, you just have to make sure they don't overlap.  In other words, this can be done without the built-in split-scope or active-passive capability.

With two servers - each with half your addresses - you'd get load balancing and fault tolerance.  Yes, if you lose a server, you lose half your scope, but depending on how long your leases are, you'd have a few days to either get the downed server back up, or re-create the missing scope on the remaining server.  

Anyway, I don't see the need to retrograde a server just for DHCP, but good luck with whatever you decide to do.

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StinkyPete1Author Commented:
You are right Paul. I just setup split scope between 2012 and 2008. I was having all kinds or errors yesterday doing the same thing, it just worked 1st try today.
Paul MacDonaldDirector, Information SystemsCommented:
Happy to help.  Thanks for the points!
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