WLANs & AP LANs

Unanswered Question
Feb 6th, 2008

I am deploying wireless to several buildings and using a wism to manage all of the AP's. I am planning to seperate all of my WLANS from my Wired lans so that each building will have 2 subnets, one for wired and the other for wireless. In the buildings, my AP's will sit on the wired lans so they can get an IP and then tunnel all wireless traffic back to the controller. However, has anyone created a WLAN and mapped it to the same vlan as the wired lan where the AP's sit and get their IPs from a dhcp source? I know it can be done because I have done it, I am just wondering if it is a best practice or a bad practice and why.

I have this problem too.
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gmarogi Tue, 02/12/2008 - 11:28

Yes, this can be done. You have something called bridge-groups. These bridge groups are used to bridge traffice between vlans and wlans. Refer ISR router configuratioon document for more information.

Scott Fella Thu, 02/14/2008 - 18:14

Since you are going to implement a centrally located WiSM, when you create a dynamic interface and assign an ssid to it, that vlan must be local to the WiSM. So depending how your network is layed out... L3 from each building or if you plan on H-REAP, you may or may not.

Layer 2 or 3: Users who associate to the access point will need to get a DHCP address from a subnet that the controller has a dynamic interface connected to. Meaning, you can't have the users obtain an ip from that wired building subnet, or else you would have overlapping subnets (one in HQ where the WiSM is and the same subnet at the other building). AP's would get an ip from the building wired subnet but users would get an ip from a subnet you would have to create locally where the WiSM is located.

H-REAP: You can have the AP's on the wired and have the users on the wireless subnet, but would have to have another dhcp scope for the wireless subnet.

Hope this helps.

jlhainy Thu, 02/14/2008 - 18:26

I do understand that, however, I have one instance where a building wired subnet is local to the wism because the wism is in the same building as the wired subnet. So, for this building, I just mapped my wlan vlan to the same vlan as the wired vlan. Everything seems to be working ok. I was just curious if this was a good idea in this specific case or should I treat this like every other building and seperate the wired and wireless subnets. I just wanted to make sure that there would be no performance problems by having the AP's sitting in the wired subnet and the wlan in the same vlan & subnet.

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