Need to Run 2 DHCP servers on the same LAN!

[colinmitton]

I currently have two sites linked by a 10mg BT LAN Extension link. So my network for both sites is infact a big LAN, I currently have a AD server on each site and want to set up a DHCP server on each site to segment my network and force each site to use there own ADSL link for internet access (a different gateway on each site) but use the other sites gateway as a back up if one fails! I currently have both sites running from one DHCP server and need to set up the second server to act as thats site DHCP server.

So the main point of my question is how do I force my clients (all XP pro sp2) to look at the relevent DHCP server for that site?

I run windows server 2003 Std have a AD domain setup and use policies. Also as a side questions could could a second scope be setup on each server to act as a backup to the other server? just in case one fails...

 

[jonhowe]

I assume that your LAN is all one IP subnet with the same addressing scheme - Is that how a BT LAN extension works ?

If so I'm not sure why you are so concerned.

Why not just set up the DHCP at both sites a don't worry.

As long as your servers do not allocate overlapping ip address ranges then you should be OK. Most of the time a local PC will talk to the local DHCP but with 10meg link surely its not a big deal if some DHCP traffic goes accross the site link ?

Jonathan

 

[porkchopexpress]

I was thinking that as well. The only problem i can forsee is forcing the alternate ADSL line when one goes down without a router.

 

[ADB100]

Why not make them 2 separate subnets and use the LES circuit as a routed link. You can then have 2 separate DHCP scopes for each network (site) and the problem has then been engineered out of the solution.....

Andy

 

[jonhowe]

Seperate subnets would be best in many ways but I think will require a router somewhere between the two sites and your BT connection might not have one you can get at.

Alternatively, assuming your ADSL routers are set as the client's gateway I think DHCP can give out more than one gateway address which would act as primary and secondary gateways.

Two subnets is best with AD as you can configure "sites" which makes all sorts of stuff easier.

 

[colinmitton]

firstly thanks for the responces.

Just to clear up the link, effectively the LES circuit does not have any routers, its like a fibre between our two offices and with out adding a router each end (which I'm trying to avoid) makes controlling traffic difficult.
Which make the separate subnet sites hard, although it may be a last resort (been thinking about that before I put the posting in)

I also trying to put a bit of a fail safe in place by minimising traffic across the link and providing each site with a working network if the link fails. i.e. each site is self suffient.

As jonathan stated in the second posting I can set up the ADSL to have a primary gateway on DHCP to ensure each IP address uses the correct router but there fore lies my original question which is ho do I get the clients to get DHCP assigned addresses from the local server first? Is there a reg hack or a policy I could use? Is there way way of setting a prefurred AD controller / DHCP server to talk with?

Thanks so far...

 

[minxca]

You can't force your client to go to specific DHCP. Remember ROSA? Request, Offer, Selection and Acknowledgement, I think if you install DHCP on each site, most of local client will go to local DHCP since the local lan at least 100Mb/s, but who knows? I have vpn tunnel and it happened few times in past that my PC was authenticated by DC from another site.