802.11b/g / PHY setting cisco 7921G

[karl.dorme]

Question:

The default PHY setting of a cisco 7921 phone is 12 Mbps.

Someone told me, that an access-point with a b/g radio can downgrades itself to b-only if it has a b-client in range.

If a cisco 7921G is configured to use the 802.11b/g band and the PHY setting is set to 12 Mbps, could this be a problem when you switch to 802.11b ?

[migilles]

Not as long as you have 12 Mbps or higher enabled. Per our deployment guide it states to design to 12 Mbps.

But if you have an 802.11b AP, then yes it will be a problem and you must either adjust the PHY rate on each 7921G phone or disable CAC.

See the 7921G Deployment Guide for more info on CAC and setting the PHY rate.

http://www.cisco.com/en/US/docs/voice_ip_comm/cuipph/7921g/6_0/english/deployment/guide/7921dply.pdf

[karl.dorme]

Yes, but all AP's are b/g...

Will a b/g AP act like a 'b' AP when there is a b-client associate on it...

If yes, I need to change all our phones...

[migilles]

Like I mentioned, if you have an 802.11b/g AP, then you don't need to change the PHY rate on the 7921 phone as long as 12 Mbps or higher is enabled.