Cisco Catalyst 4500 Series Configuration Manual page 585

Chapter 22 Configuring Resilient Ethernet Protocol
You can construct almost any type of network based on REP segments. REP also supports VLAN load
balancing, controlled by the primary edge port but occurring at any port in the segment.
In access ring topologies, the neighboring switch might not support REP, as shown in
Starting with Cisco IOS Release 15.0(2)SG, you can configure the non-REP facing ports (E1 and E2) as
edge no-neighbor ports. These ports inherit all properties of edge ports, and you can configure them the
same as any edge port, including configuring them to send STP or REP topology change notices to the
aggregation switch. In this case the STP topology change notice (TCN) that is sent is a multiple
spanning-tree (MST) STP message.
Figure 22-3
REP has these limitations:
• You must configure each segment port; an incorrect configuration can cause forwarding loops in the
networks.
• REP can manage only a single failed port within the segment; multiple port failures within the REP
segment cause loss of network connectivity.
• You should configure REP only in networks with redundancy. Configuring REP in a network
without redundancy causes loss of connectivity.
To use REP effectively, you should understand the following topics:
• Link Integrity, page 22-4
• Fast Convergence, page 22-4
• VLAN Load Balancing, page 22-4
• Spanning Tree Interaction, page 22-6
• REP Ports, page 22-6
OL-25340-01
Edge No-Neighbor Ports
E1
E1 and E2 are configured
as edge no-neighbor ports
E2
Software Configuration Guide—Release IOS XE 3.3.0SG and IOS 15.1(1)SG
REP not
supported
REP ports
About REP
Figure 22-3.
22-3