Cisco ICT Trunk incoming call flow

[abhishek169]

I would like to know how the incoming call from one call understand that it needs to use the exact trunk on the another cluster in ICT is there a mapping of something that it checks in another cluster....Let's say if i have CUCM 1----ICT1..... Ougoing number.>>>>>> incoming number to CUCM 2 maps 

I mean generally we have CSS maps to partition and partition maps to Translation(if any) based on the partition of the calling search space and then the Route pattern with matching partition.So, similarly how the ICT maps happens in another cluster can anyone give more explanation how the incoming call from other cluster is compared in the receiving cluster 

I only know there is exit point of destination from the source cluster and destination cluster how returns the traffic back need some logic that would be greatly appreciated. Also is there a way to see this information anywhere in RTMT when the call goes since the call flow only works for SIP, SCCP and how to check this in ICT trunk and can we trace anything for ICT traces.

[Jaime Valencia]

This is basic call routing, there's nothing special about this. You point the ICT to the IP of the other cluster, that's it.

As to calling back, same thing, absolutely nothing special about this.

Either you point to a single IP, or to a SRV which then might distribute the calls.

If you want to see this at the low level, simply review CUCM traces.

[abhishek169]

So, is the other cluster needs to point back mandatory for call to work fine or not necessary...unless the other cluster wants to call to cluster 1 DN

Just pointing the Cluster 1 to Cluster 2 is enough or is it a must the Cluster 2 should also point back to cluster 1 in destination let me know....is two trunk is mandatory is what I want to know and secondly does the call enters in destination cluster does it look for DN first or translation first if not does it look route pattern to route the call out if there is matching route...Since....let's say if I am pointing a forwarding of call to another cluster 2 DN and if there are duplicate DNs present with different partitions....how the call will flow works since there are 2 DNs with different partitions in call manager which one it will ring....?

[Deepak Rawat]

No, it is just not enough to create an ICT on Cluster 1 pointing towards Cluster 2. You will need to create an ICT on Clutster 2 as well pointing towards 1 and then only incoming calls will work since CUCM does not accept invitations from unknown hosts . Now, if you do not want users on Cluster 1 to call users on Cluster 2 but want users on Cluster 2 to call users on Cluster 1, then you will simply create a RP (which matches the Dial Plan of cluster 1) pointing to the ICT on Cluster 2 only and not on Cluster 1.

You will configure CSS information under Call Routing Information for Inbound Calls on the ICT itself which then in turn will take care of the call routing to the same DN under different partition.

Regards

Deepak