roaming between 802.11 a and 802.11g

Unanswered Question
Dec 3rd, 2007

Hi guys,

i have a question for you:


zone 1 use 802.11 a

zone 2 use 802.11 b

zone 1 and 2 adjacent and overlap also in the border line

If I configure 2 voice WLAN with the same parameters( security, auth mode etc) will a phone going from zone 1 to zone 2 continue to work?

(that is, is possible a romanig between two different radio standards)

thanks in advance.


I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (1 ratings)
migilles Mon, 12/03/2007 - 18:30

Which client is this? Is it a voice client (7921) or data client?

For 7921, can set to Auto-a or Auto-bg mode to give preference to one band or the other. Will associate to the preferred band at power up stage. But once it falls back to less preferred band it will not check the more preferred band in order to return to that band as it will not be scanning those channels until the current band's BSS is lost.

So if using 2.4 GHz for outdoor and 5 GHz for indoor, need to ensure that the SSID doesn't exist on the less preferred band where you want the client to use the preferred band.

migilles Mon, 12/03/2007 - 18:30

Also, it is possible to retain a phone call while roaming across bands in a single network profile, but can not roam between network profiles while on call.

barryfowles Wed, 08/26/2009 - 01:39

Can I just clarify this with you as I have a scenario where a customer will be using Cisco 7925 phones with 2.4GHz & 5GHz capable APs inside and only 2.4GHz mesh APs outside. If I create a single profile with 802.11a/g radios allowed, and set the phones to auto, will a phone call started inside roam outdoors (from 5GHz to 2.4GHz) OK and vice versa. If not, is there any way can I make this happen or will the call be dropped when the band changes.


alessandro.dona Wed, 08/26/2009 - 01:46

theoretically it is possible but i have never tested it and i suppose calls will suffer poor quality during roaming

migilles Tue, 09/01/2009 - 15:42

The 7925 wouldn't check to see when the preferred band comes back into range.

So you would design to have the 5 GHz signal only indoors and the 2.4 GHz only outdoors.

There would be a small gap when transitioning across bands, but it will retain the call assuming the SSID is the same for indoors and outdoors and the phone can use the same IP address.

More info in the 7925G Deployment Guide on page 51 @

barryfowles Thu, 09/03/2009 - 01:54


Does your recent reply apply to my post above or the original post? I will have the 802.11a/g bands indoors but only 802.11g available outdoors (via mesh). The customer wants to know what happens when a 7925 phone on a call roams from indoors to outdoors and vice versa. Is there a recommended setting for the phone and config for the WLAN to cover this?

amr.momtaz Sun, 05/09/2010 - 10:32

The answer to your question is YES.

I configured the same deployment, and it is working with no problems at all, the roaming between the 802.11g and the 802.11a is treated as it is a normal L2-Roam. No additional configuration is needed. Just make sure that the phone is set to the default Wlan settings; "Auto-RSSI: which will search for a SSID with the configured parameters (name, security settings) and connect to whichever signal it receives"

Check the attach file for the rest on how to configure the Wlan settings for the IP Phone.



This Discussion