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Unable to configure clocking on a 7200 router that uses the PA-A3-8T1IMA port adapter

Core Issue

The issue occurs when an Asynchronous Transfer Mode (ATM) exists in the 7200VXR and attempts are made to set an external clock or clock from the line, but the clock status appears to still be internally clocked.

In order to confirm the Cisco 7200VXR series router system clocking, issue the show network-clocks command. This is an example of the command output:

Router#show network-clocks
Priority 1 clock source: not configured
Priority 2 clock source: not configured
Priority 3 clock source: not configured
Priority 4 clock source: not configured
Priority 5 clock source: Local oscillator
Current clock source:Local oscillator, priority:5

Cisco Bug id CSCse75697 identifies this issue.


In Cisco IOS  Software Release 12.4(10.4)T and later, these are the defaults and clocking features for the PA-A3-8T1IMA port adapter.

Refer to Cisco Downloads in order to obtain the appropriate Cisco IOS software release.

Issue the show controller atm [slot/port] command in order to see the value of txtiming, which indicates the current clocking status.

  • If txtiming is 0xA, it indicates line clocking.

  • If txtiming is 0xE, it indicates internal clocking.

The show network-clocks command is not supported on 7xxx platforms for the Inverse Multiplexing over ATM (IMA) port adapter. Because of this, the clocking on these interfaces defaults to line.