Showing results for 
Search instead for 
Did you mean: 

G.729 over IPSEC Tunnel?

Marcus Olson

How would I specify my UC560 to use G729 over IPSec tunnels instead of G711?  I have multiple home users with IPSEC tunnels to the UC560 for home phones/telecommuting.  I'd like to still use G711 for internal dialing, but if I can't i'm fine with using 729 across the board.

I'm having issues where some remote users get choppy calls and distortion until they mute the phone, then unmute it.. then the distortion stops.  I've tried packet prioritization, rate limiting for everything but VOIP/SIP traffic.. issue still persists.  I even upgraded from a UC520 to a UC560. 

Any insight would be great.  Thanks!          

8 Replies 8

Darren DeCroock


If you want to specify a certain codec for those users, you can do this by hard coding the codec on those user's ephone.

This option will be available in CCA 3.1, but currently you would have to modify the ephone though CLI.

Thank you,



Hello - do your mean mute/un-mute or hold/off-hold ? Does the call stay clear after the operation ?


Sorry, yes.  Hold/Unhold.

I have a wav file of the sound.  Its really strange..  wish I could post the sound file here.              

I seem to have less issues with VOIP 'quality' when remote users are using 871's,  when I deploy an ASA it seems to have more issues.  Is there any reason that might be? 

Whats the best way to improve performance for two remote users calling each other? It makes a direct connection once the call handling is completed by the UC560 right.  So right now the users can get to each other but they all route through the hub (aka the tunnels that terminate at the uc560) would it make sense to have a tunnel from each user to each user to eliminate that hop?  That would be a management nightmare but the users are at their wits end with the system.

Each end user has a 5mbps/20mbps Comcast Business Cable connection.  Which I've done 1080i tandberg video conferencing coast to coast with, without issue.

The only thing I can think of, which sounds 'remotly' (no pun intended) like what you describe is a problem with comfort noise and g729 a/b mismatching. - but you say you're doing g711. There's a fix for the g729ab  - voice class codex annex b all - under a dial peer or global config....

Hi guys

In the back of my mind,  you are using by default a  low compression codec G.711 and getting poor voice quality, maybe packet drops  what ever causing this.

It would be interesting to see what effect a high compression codec like a G.729 will have on voice quality,  if voip packets still get dropped. Voice quality may be worse.

In my mind I am thinking what is so different between the configuration on a CCA supported SR520 OS router at a teleworker location compared to the configuration on a 871. Both are basically ISR fixed cofig routers.

See if the technical enablement lab on multisite provides some clue. The comment at the bottom of the lab suggets;

The VPN works great but we need to add to this document that each phone behind the SR-520 must be defined as a Teleworker in CCA or add MTP to each phone through CLI.  I was having audio problems when this was not set for the phones behind the SR-520 at the remote locations.

Below if the URL that references the document.

regards Dave

Thanks David.  I have changed all the prefered codecs to 711 but the issue still occurs.  I have ipsec tunnels to each device just hard coded (vs using EZVPN). The configuration results are identical when compared to the document.  I didn't see any special QoS/Rate limiting/etc/etc ...  so the only thing that might work is MTP.  I however do not fully understand how to configure MTP or how to 'enable it' on a phone.

I read through that to get an understanding of it but it seems like it could very well be the issue as it relates to voicemail as the issue is apparently more 'noticable' when dialing voicemail as the client has told me and its possible the voicemail codec is different then the prefered codec of 711?          Any insight would be huge.

Hi Marcus,

I would like to go totaly left field on this one, just as an exercise if you are prepared to do it

Can you force the iLBC Codec across the board (ON all remote phones not internal ones) and let us know how the quality is, I.E Packet loss, garbled noise or voice, white noise etc..etc..

I often use iLBC to do testing, then work my way up the ladder to G.729r8 and G.729b and measure the quality differences over 10-15 calls per Codec with periods of 1-2 minutes call/talk time.

NOTE: MOH over any remote connection will sound quite ordinary, audio streaming is not the same as talking, very hard to explain this part to clients at times.



Cheers, David Trad. **When you rate a persons post, you are indicating a thank you or that it helped, but at the same time you are also helping to maintain the community spirit - You don't have to rate posts and you wont be looked down upon :) *
Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: