non-broadcast ssid = no beaconing?

[huangedmc]

We were told that even though Cisco AP's can support a ton of different ssid's, it's a good idea to keep that number to minimal, due to the fact that each ssid becons to the lowest data rate.

Does anyone know what the recommended max. number of SSID is?

Also if we simply make the SSID non-broadcast, does the AP still send becon out for that non-broadcast ssid, and therefore make it somewhat better?

[Surendra BG]

Hi,

On Cisco Access Points max number of SSID is 16.

SSID Non Broadcast is Not the same as no Beaconing..  Beacon contains SSID as a field inside it..

I mean Beacon contains SSID as a field inside it.. and if ur not braodcasting , then that field will be 0.

Yes Hiding the SSID is a god option!!

Please dont forget to rate the usefull posts!!

Regards

Surendra

[huangedmc]

Thanks for the quick response.

What I was trying to ask though, is if having multiple SSID's would have a negative impact on performance, and if making them non-broadcast makes it any better?

[Surendra BG]

The max that we can configure on the AP is 16.. So nothing will happen and it wont impact... hiding the SSID will not help to be frank!! its jus a security feature.

Regards

Surendra

[George Stefanick]

Its very rare that I disagree with Surendra, but this time I might have to. Sorry buddy...

Your concern is a legit one. As you add SSIDs these SSIDs will beacon and as such take up air (medium). If you have a dense wifi environment with 1 PHY rate mandatory this means beacons will be sent very far and very slow. What happens to your available medium or shall I say channel utilizationwill increase.

In fact, in voice density networks, you can see a 35-50% channel utilization with NO traffic with excessive ssids and 1 PHY rates.

Do this as a test. Take just 1 ap and add 16 SSIDs. Your channel utilization will be 25-35% with no traffic. Thats JUST BEACONS.

My advice, the less the better and never more than 8. Also move up your mandatory to 5.5 or 11 and kill 1 and 2.

Please rate helpful post !

Thanks..

[Surendra BG]

Ha ha Very nice points!! 5+

[huangedmc]

George,

Is this less of an issue if we set the SSID's to non-broadcast?

Surendra said the ssid field in the beacon would be set to 0 if it's non-broadcast; what does that mean in terms of the channel utilization issue you mentioned?

[George Stefanick · Accepted solution]

Lets be clear what a broadcast is and a beacon is ...

Aps need to beacon. If they do not beacon they dont work cause clients will not know where to find them. With that being said, if you enable 16 SSIDs you will have 16 beacons. These are virtual btw. Also they will all use medium.

If you want to know about the virtual beacons and cisco check out my blog post:

http://www.my80211.com/home/tag/cisco-virtual-mac-address

Broadcast / Hide your SSID

There is a field in the beacon that holds your WLAN SSID. You can either hide this or reveal it. If you hide it you lessen the chance of devices finding it. But as Surendra pointed out there is no real security. Becuase there are ways to get the hidden ssid.

So if you hide it or no, no impact to your medium at all.. Why, beacuse the APs still need to beacon ..

Make sense now bud?

[huangedmc]

Thank you George

[Surendra BG]

Lemme be frank... i just enjoy being in this forum.. coz i can see and learn few things that are very precise!! like  the way u answered this post!!

[George Stefanick]

I have nothing but love for you BG ... I also know you guys are locked away in cubes and have almost no time for field work. Ive learned more from you than you know! I appreciate you!

Now rate some of my post cause Steve is catching up to me !

[Surendra BG]

ha ha Did  the same!!

Regards

Surendra