I had configured four PRI in single router for ISDN connectivity. At some extends both incoming & outgoing calls had stopped suddenly from all the PRI. I had troubleshoot following steps to bring PRI connectivity but no use
1)Checked the status of PRI's - Both Layer 1 is active and Layer 2 is Mutliframe Established
2)No calls has established by self dialing also.
3)CPU utilization is under control.
Finally after restarting the router all ISDN channel started working normal.
Can anyone suggestion what might be root causes for this problem.