WISM uplinks per AP

Unanswered Question
May 10th, 2010

Does cisco have a reccomendation of how many uplink I should have to the rest of my network from the 6500 chasis that is housing my Wism Modules versus the number of AP's that I have?  The only thing I can find is with the 44xx series will support 48 AP's per port without LAG.  Is there a similar reccomendation for the WISM?

I have 5 Wism in a single 6509 chasis with 1 single gig uplink to the rest of the network.  I know this is not to spec so I am trying to find the exact reccomendations.

I have this problem too.
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Leo Laohoo Mon, 05/10/2010 - 15:20

Each WiSM creates 8 x 1Gb link in two etherchannels.  So that brings to 40 x 1Gb links and you have 1Gb link to the outside world?   In my humble opinion, this is not enough.  You have the following options:

1.  If your SUP720 is a VSS card, then you can use the 10Gb link.  One will do, two would be better.
2.  If you don't have 10Gb links, then you can use etherchannel and bundle up from 2-8 1Gb links.

jwinters99 Tue, 05/11/2010 - 06:02

My problem here is that I did not design this I am trying to troubleshoot it.  When I install them I provide plenty of uplinks.  Its cheap and saves on headaches such as these down the road.  Here is the situation.  This is at a college campus with roughly 2800 AP spread out through 9 wisms and 2 6509 chasis each with only a 1 gig uplink to the rest of the network.  So we are talking probably at any given time 8.000 to 10,000 wireless users.   At random times the associated user will drop their connection completely and then have to rejoin.  My first guess is that the 1 gig uplink is grossly oversubscribed.  My question is this.  What happens to the AP when the link becomes completely full.  WIll it loose connection with the WLC and if so after how long of a time frame?  What is the threshhold for that ap to loose communication with the wlc?  Is there a hello packet from the ap to the wlc?  I know adding additional links is the easiest thing to do but the problem is I have no control over doing that. All I can do is make reccomendations.

Leo Laohoo Tue, 05/11/2010 - 22:51

My first guess is that the 1 gig uplink is grossly oversubscribed.

In my opinion, for every 25 APs, you need one 1Gb.  You can get away with 50 APs per one 1Gb.  But higher than that and I'd negotiate SLA because this is going to kill you.

I know adding additional links is the easiest thing to do but the problem is I have no control over doing that. All I can do is make recommendations.

Make the necessary recommendations but put it down in writing.  When the time comes, this piece of paper will be your get-out-of-jail card.

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