Cisco Catalyst 4500 Series Software Configuration Manual page 758

About REP
Figure 25-1
E1
The segment shown in
ports. The REP segment cannot cause a bridging loop and it is safe to connect the segment edges to any
network. All hosts connected to switches inside the segment have two possible connections to the rest
of the network through the edge ports, but only one connection is accessible at any time. If a failure
causes a host to be unable to access its usual gateway, REP unblocks all ports to ensure that connectivity
is available through the other gateway.
The segment shown in
In this configuration, there is connectivity between the edge ports through the segment. With this
configuration, you can create a redundant connection between any two switches in the segment.
Figure 25-2
REP segments have these characteristics:
If all ports in the segment are operational, one port (referred to as the alternate port) is in the blocked
•
state for each VLAN. If VLAN load balancing is configured, two ports in the segment control the
blocked state of VLANs.
If one or more ports in a segment is not operational, causing a link failure, all ports forward traffic
•
on all VLANs to ensure connectivity.
In case of a link failure, the alternate ports are unblocked as quickly as possible. When the failed
•
link comes back up, a logically blocked port per-VLAN is selected with minimal disruption to the
network.
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
25-2
REP Open Segments
E2
Figure 25-1 is an open segment; there is no connectivity between the two edge
Figure 25-2, with both edge ports located on the same switch, is a ring segment.
REP Ring Segment
E1 E2
Chapter 25 Configuring Resilient Ethernet Protocol
E1
Edge port
E1
Blocked port
Link failure
E2