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Problems with calls through CUSP

Hello to everyone!

I'm very new in CUSP so I have no previous experience with it. I found some configuration examples so I configured lab with Cisco Unified SIP Proxy v9.1.8 based on that examples. 

Lab is consisting of:


Phone1 (SIP) ---> CUCM1 (v10.5) --sip trunk--> CUSP --sip trunk--> CUCM2 (v11.5) ---> Phone2


I'm not sure if this scenario is supported, but if it is, here is what is happening:

1. Phone1 calls number to reach Phone2

2. INVITE from phone is sent to CUCM1

3. INVITE from CUCM1 is sent to CUSP

4. INVITE from CUSP is sent to CUCM2

5. INVITE from CUCM2 is sent to Phone2

6. phone rings, and media stream is established between Phone1 and Phone2


So far, everything looks OK. But, when user on Phone2 wants to hang up, here is a problem:

1. BYE from Phone2 is sent to CUMC2, CUCM2 responds to Phone2 with OK

2. BYE from CUCM2 is sent to itself (loop)

3. CUCM2 responds to itself with 481 Call Leg/Transaction Does Not Exists


Now, Phone2 is in hangup state (everything looks OK to user on Phone2), but Phone1 is still in call.


When I hangup Phone1, BYE is sent from Phone1 to CUCM1, and CUCM1 forwards directly this BYE to CUCM2 (no CUSP in the middle). CUCM2 responds to CUCM1 with 481 Call Leg/Transaction Does Not Exists


I have attached call flow (Phone1 to CUCM1 is not here visible as this is from CUCM2 capture).


Please, can anyone help me with this?








Can you help us understand why CUSP is placed between the two CUCM clusters in your design? That is very unusual, especially in the era of SME and/or ILS. CUSP has more obscure use cases and isn’t typically positioned as a direct replacement of an H.323 gatekeeper.



this configuration was just a lab for testing purposes and to understand how to properly use CUSP.

Main problem is that we want to upgrade our IPCC from v10.5 to v11.6 or even v12.x and in that versions outbound dialer is no longer using devices registered to CUCM. Instead, CUSP or CUBE should be used to forward calls to PSTN VGs.


However, we have some complex design with many voice gateways to different providers and used by different departments so we have to support scenario where one outbound campaign goes through one set of gateways and other campaign through others.  Because of complex design, idea is to return calls from IPCC dialer to CUCM where we allready have dialplan for that kind scenario. Also, all calls are than going through CUCM so we have them in CDR.


As I have been tested, this scenario is possible with CUBE (IPCC dialer > CUBE > CUCM > VG to PSTN) but not sure if it is possible with CUSP (IPCC dialer > CUSP > CUCM > VG to PSTN). I have tested this with CUSP but strange thing are happening.


Reason for using CUSP will be because we than don't need additional hardware, and it is easyer to do disaster recovery solution (CUSP VM backup/replication).