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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
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Chapter 17 Configuring Resilient Ethernet Protocol
Configuring REP
A segment port that is reconfigured as a spanning tree port restarts according the spanning tree
configuration. By default, this is a designated blocking port. If PortFast is configured or if STP is
disabled, the port goes into the forwarding state.
Configuring REP
A segment is a collection of ports connected one to the other in a chain and configured with a segment
ID. To configure REP segments, you should configure the REP administrati v e VLAN (or use the default
VLAN 1) and then add the ports to the segment using interface configuration mode. You should
configure two edge ports in the segment, with one of them the primary edge port and the other by default
the secondary edge port. A segment has only one primary edge port. If you configure two ports in a
segment as the primary edge port, for example ports on different switches, the REP selects one of them
to serve as the segment primary edge port. You can also optionally configure where to send segment
topology change notices (STCNs) and VLAN load balancing.
This section includes this information:
• Default REP Configuration, page 17-6
• REP Configuration Guidelines, page 17-6
• Configuring the REP Administrative VLAN, page 17-7
• Configuring REP Interfaces, page 17-9
• Setting Manual Preemption for VLAN Load Balancing, page 17-11
• Configuring SNMP Traps for REP, page 17-12

Default REP Configuration

REP is disabled on all interfaces. When enabled, the interface is a regular segment port unless it is
configured as an edge port.
When REP is enabled, the sending of segment topology change notices (STCNs) is disabled, all VLANs
are blocked, and the administrative VLAN is VLAN 1.
When VLAN load balancing is enabled, the default is manual preemption with the delay timer disabled.
If VLAN load balancing is not configured, the default after manual preemption is to block all VLANs at
the primary edge port.

REP Configuration Guidelines

Follow these guidelines when configuring REP:
• We recommend that you begin by configuring one port and then configure the contiguous ports to
minimize the number of segments and the number of blocked ports.
• If more than two ports in a segment fail when no external neighbors are configured, one port goes
into a forwarding state for the data path to help maintain connectivity during configuration. In the
show rep interface privileged EXEC command output, the Port Role for this port shows as Fail
Logical Open; the Port Role for the other failed port shows as Fail No Ext Neighbor. When the
external neighbors for the failed ports are configured, the ports go through the alternate port state
transitions and eventually go to an open state or remain as the alternate port, based on the alternate
port election mechanism.