Call flow between two cisco phones

[Horacio Gutierrez]

Hello,

If I have two  phones that use dtmf in band. if Phone 1 is one site and Phone 2 is another site that go thru the mpls cloud. Say you dial from phone 1 to phone 2 how does call initiate go from one phone to another phone what's is the process. Like is cucm or another device involved or is it an endpoint to endpoint connection. How does phone 1 know where to send rtp to phone 2 and how is dtfm use to determine where to send the call to?

[Dennis Mink]

in cucm world, phones are dumb endpoints with very little intelligence. setting up a call between two phones, be it between two locations or not, is 100% orchestrated by cucm (using sip or sccp to signal to and from phones). Cucm will provide the IP address of phone2  to phone 1 and vice versa. This way the phones set up RTP. Phones have no knowledge of each other, all dial plan and feature logic is situated on cucm.

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[Hermanus Janse van Vuuren]

Please see attached pictures for a brief explaination or example as per your question.

Voice CCIE #37771