SIP Endpoint to H.323 Gatekeeper Endpoint Calls

[jmunoz19]

Say I have a 3rd party SIP endpoint registered to CUCM.  CUCM is registered to a gatekeeper and the GK also has a H.323 endpoint registered to it.  Calls between the the SIP endpoint and the GK registered H.323 endpoint work great.

Why does this work considering that one device is SIP and the other is H.323?  Is the call actually going through the CUCM?

Thanks!

[Steven Griffin · Accepted solution]

You seem to be confusing call control signaling with the actual voice conversation. Call Manager is multi-lingual and takes care of all the signaling (SIP, H.323, SCCP, or MGCP) between any two endpoints. However, the actual voice conversation occurs between the two endpoints directly using RTP.

[JustForVoice_2]

what is the output of show gatek call from the GK.

for sure it will be H.323 to H.323

but I think the callmanager will work as CUBE in this case

[jmunoz19]

So you're saying that in this situation the CUCM may act as a MTP?

[Steven Griffin]

If the H.323 gateway had its MTP Required checkbox set and the built-in CUCM MTP was placed into the MRGL assigned to the H.323 gateway then the voice RTP stream would terminate on the CUCM and get retransmitted to the SIP device.  I am assuming a G.711 codec here.