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Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
OL-23826-09
Chapter 22 Configuring Clocking
Configuring Network Clock for Cisco ASR 901 Router
For multiple inputs having the same highest priority and quality level, the existing reference is
maintained (if it belongs to this group), otherwise an arbitrary reference from this group is selected.
QL-disabled mode
In the 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 this group), otherwise an arbitrary reference from this group is selected.
ESMC behavior for Port Channels
ESMC is an Organization Specific Slow Protocol (OSSP) like LACP of port channel, sharing the same
slow protocol type, indicating it is in the same sub-layer as LACP. Hence, ESMC works on the link layer
on individual physical interfaces without any knowledge of the port channel. This is achieved by setting
the egress VLAN as the default VLAN (VLAN 1) and the interface as a physical interface while sending
out the packets from the CPU. So none of the service instance, port channel, or VLAN rules apply to the
packet passing through the switch ASIC.
ESMC behavior for STP Blocked Ports
ESMC works just above the MAC layer (below spanning tree protocol), and ignores spanning tree Port
status. So, ESMC is exchanged even when the port is in the blocked state (but not disabled state). This
is achieved by setting the egress VLAN as the default VLAN (VLAN 1) and the interface as a physical
interface while sending out packets from the CPU. So none of the service instance, port channel, or
VLAN port state, or rules apply to the packet passing through the switch ASIC.
Configuring ESMC in Global Configuration Mode
Complete the following steps to configure ESMC in global configuration mode:
SUMMARY STEPS
1. enable
2. configure terminal
3. network-clock synchronization mode ql-enabled
4. esmc process
5. network-clock quality-level {tx | rx} value {interface interface-name slot/sub-slot/port | external
slot/sub-slot/port | gps slot/sub-slot | controller slot/sub-slot/port}