Re: DHCP through vlans

mrrlg · ‎10-03-2007

I have a 3750 switch. I am creating a wireless guest network using an ASA 5550 dmz to provide dhcp for this guest network. I have created the dmz network and placed it in VLAN 200. If I plug my laptop into a port on the switch in vlan 200 I receive the proper ip address from the ASA and am able to reach the internet. I then configured the SSID on my 1200 series aironet access point. I also configured the appropriate trunk port settings for this access point on the 3750. I know this is working properly as my corporate wpa is working on the 1200 AP. When I configure a laptop to use the guest ssid, they connect to the ap using the wep key but do not receive an ip address. There are no errors indicating that it is a wep key miss match. I have configured an ip helper-address within the vlan 200 settings pointing to the ASA but I cannot get an ip address from the access point. Would this have something to do with the fact that these are two different address ranges?

glen.grant · ‎10-03-2007

things to check would be to see if trunk is working correctly, when you have to force them on they can look like they are working when they are not . Did you match the native vlans on the WAP for the radio and the ethernet subinterface . and switchport side for the trunk ? If you do a show int trunk on the switch does it look right ?

mrrlg · ‎10-03-2007

The trunk ports appear to be working as I am able to connect via the corporate SSID on the same AP.

SSCU3750#show int trunk

Port Mode Encapsulation Status Native vlan

Gi1/0/23 on 802.1q trunking 1

Gi1/0/24 on 802.1q trunking 1

Port Vlans allowed on trunk

Gi1/0/23 1-4094

Gi1/0/24 1-4094

Port Vlans allowed and active in management domain

Gi1/0/23 1-3,10,103,200,899

Gi1/0/24 1-3,10,103,200,899

Port Vlans in spanning tree forwarding state and not pruned

Gi1/0/23 1-3,10,103,200,899

Gi1/0/24 1-3,10,103,200,899

SSCU3750#

Not sure I understand the last part of your answer. Each sub-interface on the WAP is it's own bridging group and the WAP itself is part of the same native vlan as the switch.

jcoke · ‎10-03-2007

The ASA/PIX will not accept relayed DHCP requests.

mrrlg · ‎10-03-2007

How would a computer plugged into a port on the 3750 configured as a member of vlan 200 (with an ip helper-address pointing to the ASA) be able to receive an ip address when a dhcp request coming from the WAP on a trunk port on the same switch fails? Shouldn't they both fail?