Core Issue
The clocking configuration appears to be correct. However, the show controller command shows a repeating clock slip on the E1 or T1 interface, as shown in this example:
Router#show controller e1 0/0
E1 0/0 is up.
Applique type is Channelized E1 - balanced
No alarms detected.
alarm-trigger is not set
Version info Firmware: 20020812, FPGA: 11
Framing is CRC4, Line Code is HDB3, Clock Source is Line.
Data in current interval (97 seconds elapsed):
0 Line Code Violations, 0 Path Code Violations
4 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins
4 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs
Total Data (last 14 15 minute intervals):
1 Line Code Violations, 4 Path Code Violations,
425 Slip Secs, 0 Fr Loss Secs, 1 Line Err Secs, 0 Degraded Mins,
427 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs
If a single port E1 and T1 Voice and WAN Interface Card (VWIC) is physically in WIC slot 1, and no other VWIC modules are installed, it is referred to as WIC 0. This is the case even though it is still technically on slot 1. The Cisco IOS Software configuration also refers to it as controller t1/e1 0/0.
Resolution
To resolve this common configuration error, ensure that the network-clock-participate command refers to wic 0, rather than wic 1.
This is an example of the required configuration for a 2600, with a single VWIC physically located in slot 1:
Router#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#network-clock-participate wic 0
Router(config)#network-clock-select 1 t1 0/0
Router(config)#^Z
To confirm the system clocking, issue the show network-clocks command, as shown in this example:
Router#show network-clocks
Network Clock Configuration
---------------------------
Priority Clock Source Clock State Clock Type
0 T1 0/0 Good T1
5 Backplane Good PLL
Current Primary Clock Source
---------------------------
Priority Clock Source Clock State Clock Type
0 T1 0/0 Good T1
For more information on synchronized clocking, refer to the NAS Clocking Commands section of Clock Synchronization for AS5xxx Network Access Servers.
For more background information on clocking configurations, refer to Clocking Configurations On Voice-Capable IOS-Based Platforms.
