Cisco Systems 1000 Series Manual De Usuario

Priority

External commands.

If no external commands are active, the algorithm selects the reference (for clock selection) with the 
highest QL that does not experience a signal fail condition. If multiple inputs have the same highest QL, 
the input with the highest priority is selected. For multiple inputs having the same highest priority and 
QL, the existing reference is maintained (if it belongs to the highest priority and QL group). Otherwise, 
an arbitrary reference from the highest priority and QL group is selected.

In QL-disabled mode, the following parameters contribute to the selection process:

Signal failure

Priority

External commands

If no external commands are active, the algorithm selects the reference (for clock selection) with the 
highest priority that does not experience a signal fail condition. For multiple inputs having the same 
highest priority, the existing reference is maintained (if it belongs to highest priority group). Otherwise, 
an arbitrary reference from highest priority group is selected. 

This section lists the restrictions for configuring network synchronization on a router. See 

 for 

a listing of the SPAs that you can use when configuring network synchronization.

If the network clock algorithm is enabled, use the system clock as the Tx clock (synchronous mode) 
for the Ethernet interfaces of the corresponding router. You cannot change the synchronous mode 
on a per-interface basis.

You can configure up to eight ports as clock sources on a router.

The SyncE feature coexists with SSO, but is not SSO-compliant. The clock selection algorithm is 
restarted on a switchover. During switchover, the router goes into holdover mode. 

The SyncE interfaces in the WAN mode cannot be used for QL-enabled clock selection. You must 
either use them with the system in QL-disabled mode, or disable the ESMC on the interfaces, and 
use them as QL-disabled interfaces. 

We recommend that you do not configure multiple input sources with the same priority because this 
impacts the T

SM

 (switching message delay).

You cannot implement the network clock-based clock selection algorithm and the new algorithm 
simultaneously. Both these are mutually exclusive.

The Line to External feature for clock cleanup is supported only if the line interface and the external 
interface are on the same metronome SPA.

The Line to External feature is not supported on the Cisco ASR 1002-X Router.