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Cisco IE 2000 Switch Software Configuration Guide
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Chapter 23 Configuring Resilient Ethernet Protocol
REP Segments
REP Segments
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 configure the REP administrative 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 e dge 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.

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 contiguo us ports to
minimize the number of segments and the number of blocked p orts.
• If more than two ports in a segment fail when no external neighbors are configured, one port changes
to 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.
• REP ports must be Layer 2 trunk ports.
• Be careful when configuring REP through a Telnet connection. Because REP blocks all VLANs
until another REP interface sends a message to unblock it, you might lose connectivity to the switch
if you enable REP in a Telnet session that accesses the switch through the same interface.
• You cannot run REP and STP or REP and Flex Links on the same segment or interface.
• If you connect an STP network to the REP segment, be sure that the connection is at the segment
edge. An STP connection that is not at the edge could cause a bridging loop because STP does not
run on REP segments. All STP BPDUs are dropped at REP interfaces.
• You must configure all trunk ports in the segment with the same set of allowed VLANs, or a
misconfiguration occurs.