WDS - How many WDS APs can there be?

[marcbutler]

Hello All

I hope that someone can shed some light on this for me.

I am looking to implement WDS for a client to make use of the Fast Secure Roaming feature (which appears to work very nicely) to solve a roaming problem that they have. However, all their 40 APs are deployed within the same Layer 3 subnet and none of them can be moved into another subnet (as they are actually looking to consolidate from two subnet into one!!). The Cisco information on this says that their can be a maximum of 30 APs within a WDS arrangement in a subnet, with 1 WDS AP and 29 "Infrastructure" APs homed to that 1 WDS AP.

Now, my question is this:

Is it possible to have two (2) WDS APs within the same subnet, both having , say, 19 "infrastructure" APs being homed to each, and each of the WDS APs forwarding EAP authentication requests to the RADIUS server?

Any info that you could give on this would be much appreciated.

MAny thanks

Marc

[rmiles]

I have never tried setting two AP's as masters, but I would assume it will fail. I have been told by TAC that the recommended number of AP's running WDS is 30 when the WDS master is also serving data clients. When you designate one AP to just being the WDS master they say the limit is 60. Just a few weeks ago at Interop I was told that you can run up to 100 AP's if the master is only for WDS.

The other option, though expensive and overkill for your situation is the new WLSM module for a 6500 switch. That module also requires a SUP720 in the 6500.

With 40 AP's I would say it should work well as long as you designate one AP to only act as WDS master and not serve data clients.

[ctripp]

Hi Marc,

Mr. Miles is pretty much right on the money here.

http://www.cisco.com/en/US/products/hw/wireless/ps430/prod_technical_reference09186a00801c5223.html

Layer 2 Design

Due to access-point WDS processing and memory limitations, Cisco fast secure roaming currently

supports a maximum of 30 access points per L2 domain (subnet).

The WDS supports a single L2 domain with up to 30 access points supported per L2 domain. The 30

access point limit is not a physical limit, but is the maximum recommended by Cisco, and the maximum

number supported by Cisco Technical Assistance Center (TAC).

*When you designate one AP to just being the WDS master they say the limit is 60. Just a few weeks ago at Interop I was told that you can run up to 100 AP's if the master is only for WDS.

I have heard of this number working however this would be an untested, unsupported amount. One thing to look for on this would be if you start getting memory failures, high cpu on the WDS master you probably have too many clients on the WDS domain. This is where indeed, having one Access Point with its radio shut off to minimize memory usage would probably increase the number of APs you could effectively add.

You cannot have two WDS masters on one subnet. Even if you were to select two masters to have the same priority the selection algorithm will use an alternate means to select one WDS master and designate the other as the backup.

Here is the link for the Catalyst WLSM blade.

Cisco Catalyst 6500 Series Wireless LAN Services Module

http://www.cisco.com/en/US/partner/products/hw/switches/ps708/products_data_sheet09186a00802252b7.html

Up to 300 Cisco Aironet Series access points.

Regards,

Charlie

[marcbutler]

Hey

Thanks for your input here. Most helpful.

Looks like I will go down the root of disabling the radio on one AP and use that as a dedicated WDS AP with no clients associating to it!

Now I have just got to work out how to get the APs working the way they were when they were VxWorks in that they could support 2 VLANs per SSID and let the RADIUS server take care of which VLAN a user should be assigned to!!

Many thanks

Marc