2 DHCP Servers on same network

By DoubleBarrel ·
I have 2 networks tied together with a fiber optic cable between the buildings. Both building have a wireless access point that needs to have DHCP turned on. They are on seprate numbering schemes because of access limits at the library and needing access at the City Hall. One is 192.168.0.X and the other (City Hall) is 192.168.2.X. When logging on the the Linksys in city hall the DHCP comes from the Library's Belkin. Is there any way to control this. Laptop we used for testing was XP Pro and the one time we tried it with a Vista laptop it worked OK but the Vista laptop is the one used to program the Linksys router in city hall while hardwired.
Any ideas out there in the land of wisdom?

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Couple of thoughts

by robo_dev In reply to 2 DHCP Servers on same ne ...

Clarify about 'wireless Acces Points' that have DHCP turned mean wireless routers, no?

How do you get to the Internet...which router?

While obviously it would make sense to do this the right way, by putting a router between the two networks, you may be able to make this 'less broken' by:

Assign static IP Addresses in workstations that need to work.

DHCP reservations may help a little bit, but only for wired workstations. This won't help wlan clients if they can reach either AP.

Control what access point workstations can connect to via security settings, radio channel, and workstation settings.

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Stop using Consumer level stuff...

by CG IT In reply to 2 DHCP Servers on same ne ...

Sorry but using consumer level equipment in a government institution is just asking for security problems.

The question, 2 DHCP servers on the same subnet, you can use a superscope with 1 DHCP server. however as anyone in IT infrastructure knows, you can only have 1 DHCP server on a single subnet. you can put 2 in there but you can't tell clients to use on over the other. Need that? create a seperate subnet.

Want directed traffic, use a linux box and program it.

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Well put

by robo_dev In reply to Stop using Consumer level ...

any other solution is like putting some Neosporin on a gaping head wound....

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by teh_tr_monk In reply to Stop using Consumer level ...

continue to use consumer level products but with advanced firmware. For example, a WRT54GL with DDWRT firmware. Nice.

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Thanks for the comments so far

by DoubleBarrel In reply to Or...

Yes, they are routers and they are behind a main router. If I had any control over what they purchased it would have been nice. It would be great to not have to fix other peoples stuff. We can't use static IP's because both routers are in seperate buildings and provide access for the community meetings as well as the one in City Hall being used for City Manager's laptop. (That could be locked static but he travels with it as well)

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you can't have 2 DHCP servers on the same subnet

by CG IT In reply to Thanks for the comments s ...

you can have 1 DHCP server and use a superscope

here is a MS Technet article on superscopes.
while this is for W2008 server the principles are the same for W2003 and lower.

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The best thing might be to shutoff the router part of the wireless routers

by robo_dev In reply to Thanks for the comments s ...

A wireless router is just an Access Point and a router in one box.

An AP is a mac-layer bridge, so any wireless workstations will use whatever DHCP server is on the wired network.

To make a router into an AP, just turn off DHCP and connect one of the LAN ports into the existing LAN. Set a static IP address within the same IP range of the LAN so you can get to the web config page of the unit.

Assuming that there is a Cisco router or Microsoft server on the network, use that for DHCP. Microsoft's DHCP server is fairly easy to setup, and you can do fancy things like superscoping, etc.

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humm if you must have WiFi routers instead of APs

by CG IT In reply to The best thing might be t ...

then simply create subnets. If users must traverse the subnets, then using routers, expecially consumer level routers is not the way to go. That's because users traversing routers do so as remote access clients (through PPTP or L2TP or other remote methods. To gain access to the LAN must have a local address. That requires DHCP relay agent and consumer level routers typically don't have that capability.

So as robo_dev mentions, simply bypass the routing function by only using the routers built in switch [and not the WAN port].

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Try Superscope and dhcp relay

by mwalsh In reply to 2 DHCP Servers on same ne ...

Here try this article. then at the bottom click the article about relay servers

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Thanks to all for the fine help

by DoubleBarrel In reply to Try Superscope and dhcp r ...

I am turning off one of the DHCP servers for now. I am putting a new 2008 server in in a couple months and can resolve the problems then. They are running a 2000 box (old) now for a server and are wanting too much flexibility for the equipment. Never hurts to ask questions to see if there's any magic out there. They'll just have to wait. Thanks again for all the suggestions.

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