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New Member

G.729 pre-ietf codec problem

My problem is basically that codec G.729 pre-ietf (no standard) gets negotiated randomly, even when I explicitly setup G729 on the config side.

I dind't find any clue at

Any suggestion ?

Note: im using c3600 series with NM-HDV loaded. IOS 12.2(11)T IP Plus


Re: G.729 pre-ietf codec problem

you can create a 'dummy dial peer' that will force the router to always use particular settings -

dial-peer voice 1 voip

incoming called-number .

codec g729r8

ip precedence 5

Put this at the top of the dial peer list (IOS hunts through dial peers top down) and the 'incoming called-number .' matches on the inwards call leg and then applies the configured settings for the call leg.

New Member

Re: G.729 pre-ietf codec problem

The codec is forced, but from time to time some calls fall into g729 pre-ietf.

New Member

Re: G.729 pre-ietf codec problem

I get this a LOT. I'm running a VG200 with NM-HDV, IOS 12.1(5)T9. Just switched from CAS to PRI signaling. Configuring a answer-address voip peer helps, but still doesn't alleviate the problem. (No I'm not upgrading IOS yet, 12.2 breaks my PRI setup for some reason)

I have the following setup:

voice class codec 99

codec preference 1 g711ulaw

dial-peer voice 9 voip

answer-address *T

voice-class codec 99

ip precedence 5

That should force EVERY voip call leg to be negotiated at g711ulaw. Doesn't work for some reason. Still get a lot of pre-ietf legs that result in busy signals. From what I've been able to find out, the pre-ietf codec is the default for when it can't/doesn't negotiate the codec properly. Seems that we should be able to define the default so it doesn't fall back to this (un-supported) codec.

New Member

Re: G.729 pre-ietf codec problem


I've solved my problem by changing some lines in the config.

Did you try replacing answer-address by incoming-called number ?


New Member

Re: G.729 pre-ietf codec problem

From what I read about the command on CCO, it is not applicable to what I'm doing. I'm running H.323, no modems, so no application to forward to.

What the answer-address command allows you to do is setup parameters for the voip leg of any pots call. Should keep any ambiguity about what codec to use out of the equation. Doesn't though

New Member

Re: G.729 pre-ietf codec problem

Im using voice too, not for dialup.

Im using incoming called number for DID and it works perfect

Hope to be useful


Re: G.729 pre-ietf codec problem

When a voip call is made, there is a forward call leg and a return call leg from the other device. Each call leg has to negotiate the capabilities. By creating a dummy dial peer with 'incoming called number .' , the return call leg will match on this dial peer and use the parameters configured under it, so you can control VAD, DTMF relay, codec selection, precedence/DSCP of return packets etc ... Give it a try and see if it help.

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