Solved: WDS questions

mccullrrcisco · ‎08-10-2007

Hello all,

I am setting up a campus dorm with wireless AP's. I have decided to make one primary WDS and one backup WDS.

My first question - Is the backup WDS configured exactly like the primary WDS except for the priority number?

Second question - If a user is connected to an access point and the primary WDS goes down, will the user lose connectivity until the secondary WDS comes online?

Thanks for your help!!

Becky

Rob Huffman · ‎08-10-2007

Hey Becky,

No worries :) The user will need to re-auth in this scenario, just like you have seen in your testing. I wouldn't worry too much about that though, this stuff is pretty stable.

Good luck with your deployment!

Rob

View solution in original post

Rob Huffman · ‎08-10-2007

Hi Becky,

You are correct here :) The Primary or WDS Master will have a priority of perhaps 254 and the backups will be the same but with a lower priority number like 250 and 240.

If a user is connected to an Infrastructure AP and the WDS Master goes down they will not lose connectivity but there may be a bit of a hit on roaming until the Secondary WDS takes over (should be very quick).

Here is some other info;

The WDS device performs several tasks on your wireless LAN:

Advertises its WDS capability and participates in electing the best WDS device for your wireless LAN. When you configure your wireless LAN for WDS, you set up one device as the main WDS candidate and one or more additional devices as backup WDS candidates. If the main WDS device goes off line, one of the backup WDS devices takes its place.

From this good doc;

http://www.cisco.com/en/US/products/hw/wireless/ps4570/products_configuration_guide_chapter09186a0080341d2d.html#wp1035881

Q. How many WDS backup candidates can I have? Can a WDS backup candidate still function as an AP in the WDS and report the information to the primary WDS?

A. There is no limit to the number of WDS backup candidates. Yes, the backup candidates still function as APs that report to the WDS master. In addition, only the primary WDS AP establishes WLSE security keys and registers with the WLSE in order to interact with the WLSE. Only if the primary WDS fails, the backup WDS takes up the role of an active WDS AP and goes on to register with the WLSE and establish security keys. As long as the primary WDS is active, the primary WDS functions as a normal AP that reports to the WDS master.

Q. If I have three WDS APs and they all fail, does the failure only affect WDS information, or all APs and clients? In other words, is the WDS a point of failure for the wireless network?

A. If your WDS masters fail, all APs fail as well. However, if the APs have all the configurations that are necessary for the AP to function independently, the APs begin to work without the WDS when the WDS device fails.

From this Q&A doc;

http://www.cisco.com/en/US/tech/tk722/tk809/technologies_q_and_a_item09186a00804d4421.shtml#qa18

Wireless Domain Services Configuration

http://www.cisco.com/en/US/products/hw/wireless/ps4570/products_configuration_example09186a00801c951f.shtml#step1

Hope this helps!

Rob

mccullrrcisco · ‎08-10-2007

Thanks Rob.

While testing the failover from primary to backup I was connected to an Infrastructure AP, I purposely disconnected my primary WDS to see if I would not lose connectivity and unfortunately I did lose my connectivity. Do you think I have something set up wrong? In order to re-establish the connection I had to disconnect to the SSID and then re-connect and then I was able to function with the backup WDS. Also, maybe I should mention that I am mac authenticating users via Cisco ACS.

Thanks again, your post is very helpful!

Becky

Rob Huffman · ‎08-10-2007

Hey Becky,

No worries :) The user will need to re-auth in this scenario, just like you have seen in your testing. I wouldn't worry too much about that though, this stuff is pretty stable.

Good luck with your deployment!

Rob

mccullrrcisco · ‎08-10-2007

Thanks Rob. You've been very helpful!!

Have a great weekend!

Becky