Cisco 3845 - Security Bundle Router Software Manual page 131

Chapter 6 Configuring Synchronous Ethernet
A REP segment is a chain of ports connected to each other and configured with a segment identifier. Each
segment consists of standard (non-edge) ports and two user-configured edge ports. A switch can have no
more than two ports in the same REP segment and each segment port can have only one external
neighbor. REP is supported only on Layer 2 trunk interfaces.
You can use REP in the SyncE network with a REP no-edge segment or with REP VLAN load balancing.
You cannot configure SyncE as a REP segment and configure a BITS interface at the same time.
SyncE uses REP only for failure detection, and not for timing topology discovery or timing loop
prevention. These SyncE features are achieved through correct configuration of port priorities. Timing
loops can occur if priority is not correctly configured.
Configuring REP allows the segment to automatically respond to a failure in the ring and avoid timing
loops by changing the direction of the reference clock path.
REP segment in a SyncE network. The 10 Gigabit ports are used to connect the switches.
After you have configured switch network clock priority and configured the REP network, enter the
ql-enabled rep-segment segment-id command to identify the REP segment to with SyncE.
Figure 6-1
Switch 3
Figure 6-2
and Router 1.
OL-23400-01
SyncE REP Segment
Switch 4
Priority 2
Priority 1
Priority 2
Blocked
Priority 2
Switch 2
Priority 2
Priority 1
Data path
Timing path
shows a failure in the timing network, a broken link in the REP segment between Switch 4
Figure 6-1
Priority 1
REP Edge
Switch 1
Priority 1
Cisco ME 3800X and 3600X Switch Software Configuration Guide
Understanding SyncE
shows how you can configure a
Router 1
REP Edge
Port
Reference
Port
Router 2
Clock
6-3