Windows Server 2003 DHCP SuperScope and DR Site

We have a DR site with a company that offer DR services.  We've se up a link wiht our Data provider  to the DR site and created a new DHCP SuperScope for the DR site in our Production AD.  

The DR company have an image of our Workstations which they restored to one of their PCs and this connected fine. i.e. it picked up a DHCP adress for the DR site and all worked as expected.  The production laptop we bought along, which 30m mins before was on our production network would not pick up a new address.  We tired ipconfig /release /renew but it would only pick up address from our Production domain and not the DR DHCP superscope.  We also deleted DNS entries for the laptop waited and was still the same.

Any ideas why this would be and how to rectify?


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Why a Superscope?

Superscopes don't contain addresses,...they only contain other Scopes,..and for the most part they are only used for Multi-netting,...and Multi-netting is a thing of the past due to the way VLANing has made Multi-netting obsolete.  In well over 10 years in the business I have never yet run into a situation where I needed a Superscope or felt it was the best approach for what I wanted to do.

A machine is only going to use the DHCP Server for the correct  "wire" that it is on.  You cannot have two competing DHCP Servers on the same "wire" unless you do not care which one the Client gets an address from, because you can not control which DHCP it gets the address from.

Sounds like you may have more than one misconception going on there and maybe more than one flaw in your attempt to do whatever you are trying to do.


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I have to agree with the superscopes statement, we no advise their use, but I don't really agree with the rest of this statement. Multiple DHCP servers can exist on the same segment, you just can use the same pool of addresses between them. The 80/20 rule for redundancy is a perfect example of this.
Since the laptop moved to a new network segment, you might expect that it would get a new IP address from the local DHCP server, but this isn't true in certain instances, especially if you are using superscopes. Superscopes effectively make the DHCP server see all the scopes under a superscope as one physical network segment. If you have a superscope setup on the production side, and it includes a scope for the DR site, it will issue the same ip address to that client everytime, regardless of the fact it is the wrong segment.
You could try setting a static address on the client, rebooting, then change it back to use DHCP and this might resolve the issue. But I think the better option is to delete the superscopes and not use them. The scopes under the superscope will not be deleted, so no worries about having to recreate everything.
I have to agree with the superscopes statement, we no advise their  use, but I don't really agree with the rest of this statement. Multiple  DHCP servers can exist on the same segment, you just can use the same  pool of addresses between them. The 80/20 rule for redundancy is a  perfect example of this.
You know,..I just got in a big argument the other day with someone twisting my words to say that I mean something other than what I meant,...well, here we go again.

I said:  
 You cannot have two competing DHCP Servers on the same "wire" unless  you do not care which one the Client gets an address from, because you  can not control which DHCP it  gets the address from.

you can have two on the same wire if you don't care what DHCP Server the Client gets an address from.

I run two DHCP Servers redundantly  and I use the 50/50 split which is better than 80/20 and the 50/50 is the more recent recommendation from MS because if you loose the "80" Server the "20" server cannot keep the LAN running as long before it maxes-out on addresses.

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Fair enough to the first point. You're right, I overlooked the "unless" so I apologize. But with 2008 R2 you can control which DHCP server responds when there is a primary and secondary in use using the new delayed response feature, but that's neither here nor there.
To the second point, 80/20 is a general recommendation for split scopes, sort of a starting point. This isn't a hard rule by any means and depends on the environment, number of clients, number of IP addresses available, length of lease, length of time to recover the primary, etc.. The delayed response feature in R2 was introduced to prevent the secondard server from exhausting it's entire pool of addresses while the primary is online, so use of primary/secondary with 80/20 split is still the recommendation as far a I know.
This isn't 2008 or 2008R2.  It is 2003.

I didn't know about the delay feature in 2008R2, but I tend to have a bit of a distrust of new features of that nature from MS and tend to design my setups to function properly and dependably without depending on those features.  If the features work, great, but I want to be "ok" even if they don't work properly.

Yes, the 80/20 used to always be the recommendation,..but that was the old MS thinking, although smoe MS employees will this tell you 80/20, just depends on which MS employee you talk to at the moment.

The later thinking is 50/50.
kswan_expertAuthor Commented:
cheers for answers guys out of the office now till mid next week will get back then.
Sure, Kswan. Sorry for the little side debate between pwindell and I, but we do both agree that superscopes are not the way to go. Deleting the superscope will not delete the scopes under it, and should clear up this issue.
And pwindell, once again you're right, Kswan is on 2003 and 2k8/2k8R2 is unrelated to the question. I went off on this tangent of controling which DHCP server responds… Anyway, delayed response is a great feature and something you might want to look at in the future as it works well.
And as far as the 80/20, with the usually disclaimer that my opinions are my own and not necessarily the views of Microsoft, I am a support escalation engineer on the networking team at Microsoft. I'm 3rd tier supporting premier customers. I'm not aware of the change in thinking from 80/20, but perhaps our pro/front line teams have a different view. I'll check into that; I'm curious where they might be getting this guidance.
kswan_expertAuthor Commented:
guys thanks for your replies to this.  we're still lookinging into this but is currently is on the backburner.  will be back with some more questions and/or points at a later date.  we'd still like to keep the question open. cheers
kswan_expertAuthor Commented:
Yeah that's fine, what i should\would have done.  cheers
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