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New Member

L3 Roaming and IP Phones Dropping call

Thought I would ask this question here.

 

Have a customer that has implemented a fairly ubiquitous wireless network in a campus environment with multiple single story houses and open areas between.  For being able to track the 7925 phones as they go from house to hose, we have the AP's in each house to be in separate VLANs but all using the same SSID for voice to make L3 Roaming a possibility.  The separate VLANs was to support CER being able to associate the correct ERLN if the phone has to do a E911 call.

 

 

problem that we are seeing is that when on a call and going between building, we will first get one-way audio and the the call will drop.  What we are seeing on the controller is that it seems to start to build the tunnel to the new receiving AP but then we see the phone go into requesting a new IP address.  Because of controller, right now we are constrained to be running 7.0 code on the AP's which are primarily 3500's

 

What I am wondering is if because of the L3 Roaming, that the audio stream is being disrupted because the tunnel is not being built "fast" enough.

 

Thoughts would be appreciated

Everyone's tags (1)
6 REPLIES
Hall of Fame Super Gold

I remembered when I had

I remembered when I had problems with 7921/7925 when running old firmwares.  The newer firmwares, 1.4(3) and newer, have improved their roaming. 

 

What exact version is your WLC running on?  And what model is the WLC?

New Member

Hi,I am the "customer" Rich

Hi,

I am the "customer" Rich posted the issue on.

WLC 5508 w/ 7.0.240.0 (secondary controller is a WiSMv1).  APs are 3502i & E -- 41 APs deployed.

7925G Firmware is current (running CUCM 10.5(1))

5508 was set up using 7925G Deployment Guide as model.  TAC also looked at settings and we made some adjustments in TPC.   No change in phone reliability..  (VoWLAN is set to only 802.11a)

Consultant performed Active / Passive Survey with AirMagnet.  Summary was that coverage "was OK".   Still experiencing poor VoWLAN.   I spent time at site last week and Using 7925G's built-in Site Survey, noticed RSSI at or near the -67 dB levels for a single AP.   Often  other APs in range are mid -70's or worse.  

Created test VoWLAN that had a single subnet.  Roaming was much better... only a single drop but several areas had poor voice quality.   No "one way audio" was noticed.   Feeling is L2 Roaming is "more forgiving" over weak signal areas-- but I believe root cause is lack of adequate AP coverage -- especially outside of these 12 buildings. 

Plan of action is to add another AP inside each of the 12 buildings.   Not sure how to attack coverage on exterior between houses.  

One question would be to upgrade code on WLC to 7.6 or 8.0 (remove WiSMv1 as backup WLC) if I can get a consensus that code would make difference based on 3502 APs being used.  

Thanks...

VIP Purple

Hi Thanks for that

Hi 

Thanks for that information & it gives us a clear picture what's going on. I agree with you on this specially if a call get dropped while you are roaming

 "but I believe root cause is lack of adequate AP coverage"

Regarding code versions & whether that will help in this case, it is difficult to say for sure.

But it is advisable to have a plan to move on to 8.x as that will be  a long lasting code. 7.0 may be there for customers who is using still old hardware, but in your case since you already have 5508, you should get feature optimization of these new software. 

HTH

Rasika

**** Pls rate all useful responses ****

 

New Member

Yes, I think that since the

Yes, I think that since the RSSI levels shown on the phone are marginal and we are rarely seeing multiple APs in a given spot with better than -67dB levels, that the added complexity of doing L3 Roaming is making the issue worse.

Based on the code in the 5508, it appears that I need to do the upgrade the Field Upgrade to  1.9.0.0.   Since I am currently running 7.0.240, do I upgrade the FUS first or the IOS?

Thanks

VIP Purple

Normally there is no

Normally there is no preference on FUS  first or IOS first.

I prefer to do IOS upgrade first in your scenario & then FUS upgrade. Keep in mind FUS upgrade will take 30-45min to complete & get enough outage window when doing both these upgrade. Also do it using CLI as you have more visibility what's going on during these FUS upgrades.

Here is the release notes for 1.9.0.0 release

http://www.cisco.com/en/US/docs/wireless/controller/release/notes/fus_rn_OL-31390-01.html

Make sure you got configuration backup on 7.0.240.0 & once upgraded compare the new backup (obviously you will see lots of differences due to feature additions, but make sure no surprise changes for the existing config features )

Also review the release notes of the IOS version you are going with as any given code having number of bugs & you have to evaluate a code with  respect to features you configured at your environment. This compatibility matrix also very useful when it come to WLC upgrade 

http://www.cisco.com/c/en/us/td/docs/wireless/compatibility/matrix/compatibility-matrix.html

Pls do not forget to rate our responses if you find them useful

HTH

Rasika

VIP Purple

HiWe will first get one-way

Hi

We will first get one-way audio and the the call will drop.

 

If your AP is operating full power (100mW or 20dBm)  & when phone is going to edge of that coverage cell, phone can hear AP, but AP cannot hear the phone (as it is max 50mW or 17dBm). That could be a reason for one way audio.

Then when client go between building, if there is coverage gap, then it is obvious client connection will drop & will associate to next building AP as new connection (no roaming).

So you should ensure AP operate in max power of 17dBm ( TPC max for 802.11a/n band set to 17, default 30, assuming phone is working on 5GHz). Also ensure overlapping coverage for seamless roaming.

As Leo said, make sure 7925G having latest firmware as well.

HTH

Rasika

**** Pls rate all useful responses ****

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