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Connecting CM to SIP Trunk provider

I am getting ready to bring a CM 9.1 system online for my group.  We will be going through a SIP Provider for phone service.  From the reading I have done I know I have three ways of connecting to a SIP Provider -

1) Directly to CM Server

2) Router serving as a voice gateway

3) Router running CUBE to connect to SIP provider

Higher ups feels that since we are connecting to a single SIP provider that using CUBE isnt needed.

From previous forum posts, I understand that connecting directly to CM server isnt recommended and isnt best practice.  I get that.  I am pushing back on using that as an option.  I have a few questions that I would like some help with -

1) If we terminate the SIP Trunk to an ASA and then pass the traffic through to the CM server, is that ok ?

2) Since we are just going to do voice traffic at this point, would a router functioning as a voice gateway work ?

3) Been trying to find a document that helps me understand the difference between a router functioning as a voice gateway or CUBE. 

Would appreciate any assistance,


VIP Super Bronze

Connecting CM to SIP Trunk provider


You cant terminate sip trunk to an ASA. You can have ASA between CUCM and your provider but thats is another headache. You need to know what you are doing for this to work very well. I dont recommed terminating sip trunk directly between CUCM and ITSP

You can only use CUBE and not an ordinary voice gateway. CUBE is a voice gateway, however you can have voice gateways that are not acting as a CUBE..

A CUBE basically allows ip to ip connection, while a traditional voice gateway allows IP to TDM IP to TDM PSTN.

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Cisco Employee

Connecting CM to SIP Trunk provider

A voice gateway will act like a cube if you allow ip to ip connections under voice service voip..

CUBE is basically used for address hiding and connect two voip legs (sip to sip or h323 to sip or vice versa..)

so depending on the protocols you are going to use, you may allow those connections using below command on a voice gateway.,

voice service voip

allow-connection sip to sip

allow-connection sip to h323

allow-connection  h323 to h323

allow-connection h323 to h323

Hope this helps..



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