CHAPT ER
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Software Configuration Guide—Release 15.0(2)SG
OL-23818-01
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Configuring Resilient Ethernet Protocol
This chapter describes how to use Resilient Ethernet Protocol (REP) on the Catalyst 4500 series switch.
REP is a Cisco proprietary protocol that provides an alternative to Spanning Tree Protocol (STP) to
control network loops, handle link failures, and improve convergence time. REP controls a group of port s
connected in a segment, ensures that the segment does not create any bridging loops, and responds to
link failures within the segment. REP provides a basis for constructing more complex networks and
supports VLAN load balancing.
This chapter includes these sections:
About REP, page 20-1
Configuring REP, page 20-7
Monitoring REP, page 20-14
Note For complete syntax and usage information for the switch commands used in this chapter, look at the
Cisco Catalyst 4500 Series Switch Command Reference and related publications at this location:
http://www.cisco.com/en/US/products/hw/switches/ps4324/index.html
If the command is not found in the Catalyst 4500 Command Reference, it is located in the larger Cisco
IOS library. Refer to the Cisco IOS Command Reference and related publications at this location:
http://www.cisco.com/en/US/products/ps6350/index.html

About REP

One REP segment is a chain of ports connected to each other and configured with a segment ID. Each
segment consists of standard (non-edge) segment ports and two user-configured edge ports. A switch can
have no more than two ports that belong to the same segment, and each segment port can have only one
external neighbor. A segment can go through a shared medium, but on any link only two p orts can belong
to the same segment. REP is supported only on Layer 2 trunk and PVLAN promiscuous trunk interfaces.
Figure 20-1 shows an example of a segment consisting of six ports spread across four switches. Ports E1
and E2 are configured as edge ports. When all ports are operational (as in the segment on the left), a
single port is blocked, shown by the diagonal line. When there is a failure in the network, as shown in
the diagram on the right, the blocked port returns to the forwarding state to minimize network disruption.