DHCP Blocked by VLAN

Answered Question
Jan 23rd, 2012

We have a server that we remove from the rack. The only role it has is to give out DHCP on the wireless network. I tried enabling  the built in DHCP server on  the Airespace 4112, though a Catalyst 3750G, but I dont get an address when I'm connected to the wireless network even though the range is enabled. If I set an static IP on my wireless card I can access the network. I also tried enabling DHCP on a Sonicwall that is connected to the Catalyst 3750G.

Do I need to link the DHCP scope to the wireless network?

Is there anything on the switch that would be blocking DCHP since it on a VLAN?

I have the last four ports in a VLAN for the AP's and the internet connection to the Sonciwall.

Thanks fort the help.

I have this problem too.
0 votes
Correct Answer by cadet alain about 4 years 9 months ago


go to the interface VLAN where your client are and modify the ip helper-address if necessary.



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Overall Rating: 5 (1 ratings)
sleepyshark Mon, 01/23/2012 - 11:59

Did you delete the existing DHCP scopes on the server?  Also, what was the old IP of the server?  When you re-added it to the network did you use the same IP address?  Have you made any other changes to the server/network (particularly network/gateway/routing changes)?


Sean Brown


airiedemann Mon, 01/23/2012 - 12:06

I didnt delete the scope I just unplugged the server so it wouldnt give out DHCP.

I didnt re-add it since I want to use the Airespace built in DHCP server. For now we have the old server plugged in giving out DHCP till I can track down why the only thing that can give out DHCP is the server.

cadet alain Mon, 01/23/2012 - 13:22


is the DHCP server on a different subnet than the clients? if so have you updated the ip helper-address to point to the new DHCP server? and also does the new DHCP server knows how to get to this subnet( with a static route for example)?



airiedemann Tue, 01/24/2012 - 14:11

Ill check the server but I'm pretty sure that its on the same subent.

Where do I update the ip helper-address?

Correct Answer
cadet alain Wed, 01/25/2012 - 09:43


go to the interface VLAN where your client are and modify the ip helper-address if necessary.



airiedemann Fri, 02/10/2012 - 10:21

I ended up using the override DHCP option in the Airespace and pointing the ip to itself.


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