CHAPTER
1-1
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-25303-03
1
Configuring Resilient Ethernet Protocol
Resilient Ethernet Protocol (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 ports 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.
• Understanding REP, page 1-1
• Configuring REP, page 1-6
• Monitoring REP, page 1-13
Note REP is supported on Catalyst 3750-X and 3560-X switches running the IP Base license and the IP
Services license. REP is not supported on the LAN Base license.
Understanding 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 ports can belong
to the same segment. REP is supported only on Layer 2 trunk interfaces.
Figure 1-1 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.
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