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New Member

Call refuse with message "SIP/2.0 488 Not Acceptable Media"


we have two router configured to do sip-ua a Cisco2811 and a Cisco2611XM with voice module. Everything works well on registration behaviour but when we try to call from external on the first router (Cisco2811) the call is refused with message "SIP/2.0 488 Not Acceptable Media" otherwise no problem on the cisco2611xm.

The routers have the same config.

attached the "deb ccsip mess" .Someone has an idea of the reason???



Re: Call refuse with message "SIP/2.0 488 Not Acceptable Media"

From the 2811

c=IN IP4

a=rtpmap:18 G729/8000

a=fmtp:18 annexb=yes

The SDP body in the incoming INVITE to the 2811 gateway include a field like


This will tell us that the codec to be used is G729br8 not G729r8

(G729ar8). So this needs to be fixed on the device that is sending the INVITE to the 2811.

This behavior was changed recently. Earlier, in older IOS like 123-11T, in this type of scenario we would just connect the call as G729ar8 which is the default codec on the dialpeer. But this lead to non-complaint with RFC (see RFC3555) and complaints from major SIP providers/vendors. So now, this will not work because the SIP stack in IOS

assumes that without annexb=no in the SDP - the codec is G729br8 and hence call would connect with bad audio if g729br8 is configured on the terminating dialpeer or will not connect if default codec g729ar8 is


So the key here to fix this solution is:

1) Get annexb=no in the SDP of the incoming INVITE.


2) Use 123-11T10 IOS image until you can get #1 accomplished.

New Member

Re: Call refuse with message "SIP/2.0 488 Not Acceptable Media"

I loose some point.

The IOS on the 2811 is 12.4(8). Is G729br8 codec supported or not??

if it is supported why is not used???