DHCP SBS 2008 wireless access

Posted on 2010-09-03
Last Modified: 2012-06-21
I have a server running SBS2008 and providng DHCP to 5 client machines. I have a belikin router serving as the default gateway for the network providing internet access. DHCP is disabled on the router however i have left wireless access enabled.

Is it possible to have laptops connect to the router via wireless and be given an ip address from the Server? currently it seems that clients can connect over wireless but they are not picking up an ip address.


Question by:Brandon2k1
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LVL 39

Expert Comment

by:Krzysztof Pytko
ID: 33595416
Is it possible to set on that router IP Helper pointing to other DHCP server?
LVL 10

Expert Comment

ID: 33595442
well i have tried also to do the same, but the problem is that when laptops are getting connected they will require IP first so in such case wireless router has no idea to send request to next DHCP server, there can be some wireless routers where you can mention the next DHCP server but in my case there is only option to activate wireless router DHCP. So in your case if there is no option then its not possible to have separate DHCP server other than DHCP of router itself.
LVL 17

Accepted Solution

aoakeley earned 500 total points
ID: 33595554
Can you give the exact model of the router?

If the router is simply acting as an Access Point then the wireless clients should already be getting an IP from the server.

If the router is doing "wireless isolation", or if the Wireless is on a different VLAN from the LAN, or Broadcasts from the wireless to the LAN are blocked, or something else, then the client will not be able to broadcast the DHCP request to get an IP lease.

If you provide the model of the router we may be able to have a quick look at the manual and point you i the right direction.

That being siad with the low cost of a wireless access point you may be better off buying a separate AP. This will allow you to reboot the internet router without dropping clients off the LAN.

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LVL 22

Expert Comment

by:Jakob Digranes
ID: 33595656
Aoakeley is right; as long as you don't want to separate wireless clients for the rest of the LAN, connect Belkin wireless to network via LAN ports and possibly give it a LAN IP from the same subnet as the SBS server. Then the DHCP request should be sent over to SBS server without any hassle.

Routers do not forward DHCP (or any other broadcast traffic) across VLANs/Networks (behaviour by design), if you need router functionality - then the others have a point, use either IPHelpers or DHCP Relay (tells you where the DHCP server is)

Author Comment

ID: 33596029
Thanks for the comments. I am just having a look at the points you mention. The model of the router is Belkin G wireless modem router model: F5D7634-4.

Just to clarify the router is currently on the same subnet as the LAN and is acting as the default gateway.

Would it work as a work around if i set the wireless clients with a static ip on the same subnet?
LVL 17

Expert Comment

ID: 33596590
I will look at the manual for that model....

Unless something in the router is stopping WLAN clients from accessing LAN hosts, then yes setting manual addreses may work, but not really a great solution as when prople take laptops home etc they will have to reset IP to work on home network....

Would be good to do that as a test though and see if you can ping your server....

Author Comment

ID: 33596721
Thanks, think I have come up with a work around that doesnt involve setting static ips's.

Initially I had been trying to join client machines that were not domain members. Basically it was to just give them internet access. These clients were unable to pick up an ip address.

I went on to try it with a laptop which is a member of the domain and that connected straight in via the wireless.

This got me thinking. The DNS address of the router was pointing to that of the ISP, I changed this to be the ip address of the server and hey presto both the domain members were able to connect via wifi and the non members were able to pick up an ip address and gain internet access. The server has forwarders on the dns to those of the ISP so hopefully will be no problems there.

Can anyone see any problems with this workaround?
LVL 17

Expert Comment

ID: 33596741
I have reviewed the manual for that model and cannot see anything about wireless isolation or anything to incicate that it should not pass broadcasts to the LAN. However it is quite a basic router and it may just be a 'feature' that it does not pass broadcasts on the WLAN to the LAN, thus DHCP will not work.

I know this does not really answer your question, but when you can buy an AP these days for less than $30 (australian$ wich is about 10p if you are in the UK or 50c if you are in the USA) I would still recommend using a separate AP from the ADSL router. A standard AP will pass broadcasts and thus DHCP will work and you can reboot the ADSL router without affecting wireless clients that may be accessing files on the server etc.
LVL 17

Expert Comment

ID: 33596758
nope - your solution looks fine.

It does not really answer the Q of why the DHCP did not work - but if it works for you - then Hey, it's a solution!

Author Closing Comment

ID: 33596833
I have accepted this comment as the solution as what is said is correct. The router is not performing and wireless isolation and it does work for some clients.

I dont see my comments as the solution, more of a workaround. I think in this scenario the best bet would be to go ahead and purchase a seperate AP again suggested in this comments.


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