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The Main site hosts the only Windows Server. Windows Server 2008 R2 Domain Controller running AD, DNS, DHCP, Exchange 2007. Remote site has no Windows server.

Main site subnet is 192.168.1.0/24 Remote site subnet is 192.168.2.0/24

The Windows Server at Main site is supplying 192.168.1.0/24 via DHCP to hosts at the local site where it resides. Is it possible to configure that Windows Server to supply 192.168.2.0/24 to hosts at the Remote site and if so how?

We could use the Cisco router at the Remote site to supply DHCP but if possible we'd like to use the Windows Server at the Main site to supply DHCP.

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One of the first hits for cisco ip helper on Google. routergod.com/?p=24 –  Zoredache Mar 10 '10 at 16:30
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1 Answer 1

No, not possible. As in: the remote site does not forward DHCP requests to he local site. This is becasue those are broadcast addresses which are NOT transmitted outside the Ethernet segment - i.e. they do not cross over the router.

Yes, it is possible. You need to set up a DHCP relay system on the other side (can be part of the router) to forward DHCP requests to the Windows server. Then you set up a normal segment in the DHCP server.

That said, the idea may be terrible. Problem is - whenever the link is down, and a computer gets online during this time, it ets no ip address and pretty muc hthe user needs to restart (unless you want to talk users through command line "ipconfig /renew"). DHCP has no concept (unlike IPv6 in general) for assigning addresses to computers post network activatio. Technically you would be better off to get a small servre and put it at the remote site. This can be a small ATOM based thing. This can serve as: * Local DHCP Server * Local Domain controller (same problem - link down, things get bad). * Local DNS server. * Possibly local file store, at leat for a special admin share so you have afast access to your tools.

If you dont trust the remote site, using 2008 R2 yo ucan make the controller a RODC (Read Only Domain Controller). It sitll will stabilize operations.

I would consider it bad practices to supply DHCP from your central site.

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I think the reason this whole idea came up is it seemed cheaper. It would be cheaper to use the single server at the main site than to set up a second server at the remote site i.e. purchase another license for Windows Server 2008 R2 and the client access licenses. 2008 R2 and the CALs for the remote site would be several thousand dollars. –  caleban Mar 10 '10 at 16:34
    
But... how would that be cheaper than continuing to use DHCP on the Cisco router? Is something wrong with doing it that way? Personally, I'm in the middle of deploying a bunch of dhcp servers for a corporate VOIP system. Each server is running DHCPD on CentOS, on a PowerEdge box. Our priorities weren't cost, but reliability -- with failover enabled, we'll be able to server DHCP from either each machine in the field, or from a single server in our main datacenter. –  Stemen Mar 10 '10 at 16:57
    
Not cheaper - up to the moment you have a day or two off and people can not work because you were too cheap. I also would be another backup of the domain (how many domain controllers do you run?) You run a single server? Thought about the catastrphy cost or having to COMPLETELY REINSTALL ACTIVE DIRECTORY because you dont have a single backup unit? OUCH. I mean REALLY OUCH. –  TomTom Mar 10 '10 at 19:25
    
Costs for CAL - häh? Dont get me wrong, but either the remote sytems work against your server (so they already have a CAL), or they do not (then they dont need a CAL to access DHCP). ANY single server solution sounds like "i want a desaster" for me. Sometimes you can be TOO cheap. –  TomTom Mar 10 '10 at 19:26
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