Re: 7912 gorbled voice

balukr · ‎02-04-2005

7912 phones in one of the remote location has poor voice quality , really bad and gorbled .We upgrade the 7912 firmware to 5.0 and checked QOS on the switches everything looks fine.

Funny thing is there are other remote sites with 7912 phones and has no voice issues I checked QOS and CM setup are exact replica of other sites but we have problems only on this 7912 phones .

7960,7940 works fine no problem at all.

CM version is 3.3.2 SPC

Any help would be appreciated.

smahbub · ‎02-10-2005

7912 is susceptible to broadcast and multicast traffic arriving at the switch port connected to the phone. If this traffic approaches 2 Mbps, the voice quality deteriorates.

There is known issue with 7912's. Check the bug-id CSCed27401.

balukr · ‎02-10-2005

Thanks for the info .I checked the BUG ID certain things I'm not clear on that it says it first found in version 4.0 but the bug itself says CM 3.3.3 sr3,also on the workaround looks like they are configuring auto qos which I never do for any of our customers.Did you configured that way in the switch because most of the 7912 phones are connected back to PC if you do please send me an config.

Again one weird thing is it works fine in all other remote sites with out any problem only on this particular site and only on 7912 not on 40's or 60's.

Aslo do you think we have to upgrade our CM because it is on 3.3.2 SPC?

Thanks for your help.

dgahm · ‎02-11-2005

Can you verify that the DSCP settings are correct when the packets get to your router? It sounds like you may have more congestion on the link to the site with the problem.

A 'show policy-map interface sX/X' will show you if voice packets are hitting the priority queue on the WAN link.

What model switch are you using?

balukr · ‎02-14-2005

Thanks for your help.

We put a sniffer and found out last Friday an application software was sending multicast storm and that was the one creating voice quality issues in the network.We are working to fix that now.

JASON NIELSEN · ‎06-13-2005

Cisco has released a new phone, the 7912i that resolves this issue. We have used the storm-control on the interface level of the switch to supress multicasts. This has worked for us. We are now getting the 7912i's.