Windows Server 2012 DHCP Failover

Hi,

We are looking to move to server 2012 to benefit from the DHCP failover. Would the following scenario work?

Site A:
2x DHCP Servers on 10.16.x.x
Failover partnership for these ranges

Site B:
2x DHCP Servers on 10.10.x.x
Failover partnership for these ranges

So the question are:
Can I setup another partnership between the servers at each site as a hot standby aswell, which will then replicate to the 2nd server on the site?

Are the partnerships limited due to scope ranges? so I can I have a dhcp server thats in a partnership with an onsite 2nd server for the whole ip range e.g 10.10.x.x, then have the other site as a hot standby for the same range?

Would having 1x DHCP scope at each site and setting up 2 hot standby relationships for each other site wise be a better option?

Thanks and hope it makes sense!
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Colchester_InstituteAsked:
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Will SzymkowskiSenior Solution ArchitectCommented:
Are the partnerships limited due to scope ranges?

There is no limitation for this. You can have multiple scopes you just need to make sure that you address this in the partnership setup/config.

so I can I have a dhcp server thats in a partnership with an onsite 2nd server for the whole ip range e.g 10.10.x.x, then have the other site as a hot standby for the same range?

Yes you can do this as well. There are 4 configuration types for DHCP-Failover. They are below
- Simple
- Flexible
- Seamless
- Multi-Site

Would having 1x DHCP scope at each site and setting up 2 hot standby relationships for each other site wise be a better option?

You can also do this as well using the DHCP-Failover Multi-Site option. However I would prefer to have 2 DHCP servers in a failover scenario at the same site and not have DHCP requests going over the WAN. Although it can be done.

I would highly suggest you take a look at the below TechNet regarding all of the options I have listed in more detail.

https://technet.microsoft.com/en-ca/library/dn338978.aspx

Will.
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kevinhsiehCommented:
My experience is that each server can only have one DHCP failover partner. So, if you want more than two servers to be able to service a scope you will need to combine traditional split scopes with DHCP failover, or just use split scopes.
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DrDave242Senior Support EngineerCommented:
Kevinhsieh is correct: a DHCP failover relationship can include only two servers. A single server can participate in up to 31 failover relationships, but it will have only one partner in each relationship.
Site A:
2x DHCP Servers on 10.16.x.x
Failover partnership for these ranges

Site B:
2x DHCP Servers on 10.10.x.x
Failover partnership for these ranges
This configuration will work just fine, but there's no way to create an additional failover relationship between the sites. Honestly, that seems like overkill to me anyway, as the chances that both DHCP servers at a given site would be down simultaneously have got to be pretty slim (barring a site-wide power outage, but I doubt DHCP will be your primary concern if that happens).
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kevinhsiehCommented:
You are probably doing slit scopes right now. I would tend to keep the split scopes and just add the DHCP failover to those split scopes to get up to the desired 3 or 4 servers. Otherwise, I would be sure to have DHCP scopes configured on a server in site A and a second server in site B and use DHCP failover between the two. Either way is fine, but I would not leave it so that all of the DHCP servers for a particular scope are in the same site.
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DrDave242Senior Support EngineerCommented:
I would not leave it so that all of the DHCP servers for a particular scope are in the same site.
I'm curious: why not?
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kevinhsiehCommented:
Because if there is a site issue you just lost all of the DHCP servers. Maybe both servers are on the same UPS, but the network isn't. The UPS takes out all DHCP. It just seems that having DHCP available from two sites will be more resilient than two servers from the same site. Maybe you have complicated DHCP and it would be a challenge to rebuild from scratch. It would be better to have a replicated copy of that offsite. None of the options are significantly better or worse.
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