Cisco Support Community
Community Member

802.11a problem


I have a 1200 AP with 5GHz module and AIR-CB0a client adapter in demo.

This all works fine (except coverage is not that good). But what I see is that when I walk arround and enter a zone with only 802.11b AP I loose my connection! So the card does not seem to switch to 11Mbit.

I saw in mij profile (ACU) that my radio Channel is set FIXED on 36.

Anybody any idea?


Koen Kips

Community Member

Re: 802.11a problem

11a devices operate at 5GHz, 11b devices operate at 2.4GHz - they will not work together.

The speed of the 11a link can only decrease while still associated to the 11a access point.

Cisco Employee

Re: 802.11a problem

Dave is correct the dual band option in a 1200 gives you 2 radio networks they are separate and you can not roam from one to the other as they are completly different radio bands

It should also be noted the range for 802.11a is approx 1/3rd of 802.11b due to the higher frequency and AP placement is more critical

Community Member

Re: 802.11a problem

Thanks for the clarification.

So I was wrong that the 5Ghz client is backwords compatible with the 2.4 GHz.


Cisco Employee

Re: 802.11a problem

Thats correct 802.11a is not backward compatiable with any other standard

802.11g which operates in the 2.4ghz band but gives a dat rate of 54Mbps is backwards compatiable with 802.11b (11Mbps)

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