Core Issue
A plan type mismatch on the gateway results in dropped calls.
Resolution
In order to fix the issue, make sure you send the correct plan type for National and International calls. To verify the call setup use the debug isdn q931 command.
Note: If you run debugs on the production router, it can degrade the performance of the router.
When you change the plan type to National, it fixes the problem.
Refer to these documents for more information:
Problem Type
Gateway or module
Call control software (CallManager, CallManager Express, ICS7750, SRST, SS7 call agents)
Call Control
CallManager
Call Connection
Call connection establishment
Dropped or disconnected calls
CallManager Features
Call routing
Call Topology and Direction
To international destination
Signaling Protocol
MGCP
TDM Signaling Type
ISDN
Voice Gateways
IOS gateways
