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GSM Codec help needed

I am trying to connect my 2851 router CME 8.6 to a service using the GSM codec.  The version they are using is

The codec is called "GSM FR" and is the 6.10 standard. The SDP line for it is "a=rtpmap:3 GSM/8000" but when I select GSM on the fouter in my dial-plan, the call rings but goes to a fast busy when answered.  When I use the G711ulaw codec (the other codec they support) calls work fine except that since I use HughesNet as my Interenet source, upstream audio is so choppy its unusable.  Downstream audio is fine.

Is htere any way I can get the version of GSM on my router to work with or be upgraded to match the "GSM FR" and is the 6.10 standard?

They do not support the G729 or IBLC codec or I would use that one.


GSM Codec help needed

GSM FR is no longer supported on ISR .

Hope this helps!



New Member

GSM Codec help needed

Is there any way to add it back?  I really REALLY need it!  I am running IOS c2800nm-adventerprisek9-mz.151-4.M3.bin

GSM Codec help needed

hi Michael,

Unfortunately there are no plans of adding support for this codec on ISR/ISRG2  .

You  could however contact your local Cisco Accounts team with your business requirements  and have them look into this.


Karthik Sivaram

GSM Codec help needed


Based on the Feature Navigator ( GSMFR isn't supported on the 2800 platform. I haven't tried to use GSM in IOS. The only time I ever came across GSM on the ISR was a HWIC module (which I believe EOL now). Also, the PVDMs in your platform do not support GSM.

So, I don't think GSM is an option for you given the current configuration. Since G711 isn't viable either then you are left with a solution that is incompatible. Which means one of the core components need to change. The carrier, the call processing platform, or your internet provider.

-Bill (@ucguerrilla)

HTH -Bill (b) (t) @ucguerrilla

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