Unable to Call Between Clusters – Intercluster Trunk Setup Issue

[William Pacheco]

Hi everyone,

I’ve recently configured an Intercluster SIP Trunk between two CUCM clusters (Cluster A and Cluster B).
The SIP Trunk shows as "Active", but when I try to dial from a phone in Cluster A to a phone in Cluster B,
the call fails with a fast busy tone.

Any help would be appreciated

[Mohammadreza Hadi · Accepted solution]

Hi @William Pacheco 
i suggest to do this checklist:

1- Make sure the CSS assigned to the SIP Trunk in Cluster A includes the Partition of the phones (or translation patterns) in Cluster B

2- Make sure the number dialed from Cluster A matches the expected dial plan format in Cluster B

3- Double-check the following on the SIP Trunk:

Destination Address is the IP address or FQDN of the remote CUCM node (preferably Publisher or SIP-Enabled Subscriber).

Media Termination Point Required: Try enabling it for testing.

Security Profile: Ensure both ends use compatible non-TLS or TLS settings.

4- Double-check Route Pattern points to the correct SIP Trunk,
& There’s no overlapping pattern that could cause a routing conflict

5- Use Real-Time Monitoring Tool (RTMT) to trace the call & Look for any call routing rejections or digit manipulation issues.

[William Pacheco]

thanks @Mohammadreza Hadi 

i checked CSS on both inter cluster trunk between two CUCM, and fix my problem..
issue was from wrong CSS selected..

[Roger Kallberg]

You don’t mention if you have created any call routing configuration to make calls between your clusters. A inter cluster trunk in it self does not enable call routing between your clusters, you’d need route patterns for that.

[William Pacheco]

thanks @Roger Kallberg for your attention

yes, i created router pattern between them,
but problem was from wrong CSS selected in trunk between two CUCM