Cisco Catalyst 4500 Series, Software Configuration Manual

Page: 757 / 2086

C H A P T E R
25-1
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
25
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 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.
This chapter includes these sections:
• About REP, page 25-1
•
Configuring REP, page 25-7
• Monitoring REP, page 25-14
Note For complete syntax and usage information for the switch commands used in this chapter, see the
Cisco IOS Command Reference Guides for the Catalyst 4500 Series Switch .
If a command is not in the Cisco Catalyst 4500 Series Switch Command Reference , you can locate it in
the Cisco IOS Master Command List, All Releases .
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 ports can belong
to the same segment. REP is supported only on Layer 2 trunk and PVLAN promiscuous trunk interfaces.
Figure 25-1 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.