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DTMF failing across Catalyst 4510

Last Modified: 2010-04-21
I have a Mitel 3300 IP phone controller and a NuPoint VoIP voicemail server sitting on my server subnet. I can place an IP phone on my DHCP subnet and cannot pass DTMF across to the voicemail server. If I put the phone on the same subnet as the server, DTMF has no issues and the tones work fine. I can also pass tones across our MPLS network to another phone controller that hosts that sites voicemail, but when they call back into my locations voicemail the DTMF tones do not pass across. I am doing all my routing between my local subnets through a Catalyst 4510, IOS 12.2(25). This switch also holds the MPLS routes and routes my traffic to and from edge locations. There is nothing on the 4510 that restricts traffic between subnets on the 4510.

Example subnet:  gateway is always .1 of the subnet, i.e.

All subnets on network are similar to example above.

Thanks in advance
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There are 3 ways of transmitting DTMF over a SIP VoIP connection :-

1) SIP INFO - The DTMF is contained digitally within the SIP packets themselves.
2) RTP - The DTMF is contained within the RTP packets (these are normally used for transferring voice)
3) INBAND - The DTMF is sent in the RTP packets but as normal audio

Do you know which of these methods the mitel uses?
I cant imaine it would be (1) since if it was you would not be able to make calls.
If it was (2) or (3) then if DTMF is not working I would also expect you to be experiencing one way audio aswell.


I believe that it uses INBAND but I can't be 100% sure about it. We have experienced some one-way audio issues but only when the voicemail picks up. Normal telephone conversations work just fine, no issues at all with those.
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I just received word that DTMF is transported within the RTP packets using the "MiNET" protocol. As far as I know the communication is using the MiNET protocol, not SIP.

No firewalls sit between these subnets, all routing is being done through the Catalyst 4510.

Sorry I dont think I am able to help any furthur. MiNET is a Mitel propietry protocol which I dont have any knowledge of.


Turns out the Mitel's latest version of the NuPoint voicemail server uses an embedded firewall feature (not sure if it is part of the Linux setup or NuPoint...either way) that they unfortunately forgot to put any documentation about or actually let anyone know about this feature. In other words, on the 3rd technician we talked to he was able to point us in the right direction and we solved the issue at hand. Thanks to all that replied, I appreciate your offers of help.


Thanks for your help grblades.

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