Wireless Voice Subnet Size

Answered Question
Jan 24th, 2012

I understand that a voice over wireless deployment needs its own VLAN but the question is what is the best practice size of the single voice vlan? Once exceded what is the best practice subnet size for AP Groups?

I have this problem too.
0 votes
Correct Answer by Scott Fella about 2 years 3 months ago

William,

You will get many different answers here:) So in my experience, a /24 is good, you keep the broadcast domain small. I have also had clients with a /16 and no issues, but not with voice since that would be a lot of wireless phones in general. I think the largest subnet I had wireless voice, my client was using a /23 subnet.

AP Groups woul be the same in a way, you need to define how large of a subnet you need. With the 7.0.116.0, they added a new feature called interface groups that allows you to bundle interfaces together. So you can bundle 2+ /24 if you wanted to.

Thanks,

Scott Fella

Sent from my iPhone

  • 1
  • 2
  • 3
  • 4
  • 5
Average Rating: 5 (2 ratings)
Correct Answer
Scott Fella Tue, 01/24/2012 - 17:43

William,

You will get many different answers here:) So in my experience, a /24 is good, you keep the broadcast domain small. I have also had clients with a /16 and no issues, but not with voice since that would be a lot of wireless phones in general. I think the largest subnet I had wireless voice, my client was using a /23 subnet.

AP Groups woul be the same in a way, you need to define how large of a subnet you need. With the 7.0.116.0, they added a new feature called interface groups that allows you to bundle interfaces together. So you can bundle 2+ /24 if you wanted to.

Thanks,

Scott Fella

Sent from my iPhone

Leo Laohoo Tue, 01/24/2012 - 17:46

Depending on the uptake of your Wireless VoIP.  Ours, for example, is /25. 

George Stefanick Tue, 01/24/2012 - 18:24

Scott hit the nail on the head ..

My deployment has 3000 phones in one subnet with no issues .. Although I would not recommend that large of a subnet . I would do /22. Just more manageable.

The wlc doesn't send broadcast so you can get larger subnetworks when compared to wired.

Sent from Cisco Technical Support iPhone App

migilles Tue, 01/24/2012 - 18:35

We do not have a hard rule on how large a voice client subnet should be in our VoIP or VoWLAN documentation.

But rule of thumb is to not exceed a /22 as mentioned above. 

/24 would be a more preferred size from a wired VoIP perspective, but with VoWLAN, that # can be exceeded very quickly in a single deployment (e.g. 500+ size 792x deployments).

I will probably add this to the next rev of the 792xG, 9971 and Cius Deployment Guides.

There are minimal broadcasts coming from our Cisco WLAN endpoints (e.g. 792x); just the occasional ARP, CDP, etc.

Use of multicast could also influence the subnet size as well.

f.meixner Sat, 07/07/2012 - 13:13

Can you specify, when the next revision of deployment guides will be available, especially for 792xG v1.4.2?

migilles Sat, 07/07/2012 - 15:29

Hello Felix.

Hope things are well.

I have been working on syncing the 7921 & 7925/7926 guides with the Cius guide as well as new detail.

Hopefully in the next few weeks I can get something posted.

However the core detail will remain the same and all will apply to 1.4(2) and 1.4(3) except for channel parking.

You have my email address, so ping me if you need more info.

Sent from Cisco Technical Support iPhone App

migilles Thu, 08/16/2012 - 07:56

The updated Deployment Guides for Cisco Unified Wireless IP Phone 7921G and for the Cisco Unified Wireless IP Phone 7925G, 7925G-EX, and 7926G are now available on Cisco.com.

7921G Deployment Guide – 1.4(2) Update

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

7925G, 7925G-EX, and 7926G Deployment Guide – 1.4(2) Update

http://www.cisco.com/en/US/docs/voice_ip_comm/cuipph/7925g/7_0/english/deployment/guide/7925dply.pdf

Sent from Cisco Technical Support iPhone App

Actions

Login or Register to take actions

This Discussion

Posted January 24, 2012 at 5:32 PM
Stats:
Replies:8 Avg. Rating:5
Views:2368 Votes:0
Shares:0
Tags: No tags.

Discussions Leaderboard