Specifications

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Cisco MWR 2941 Mobile Wireless Edge Router Release 3.5 Software Configuration Guide, Cisco IOS Release 15.1(3)MR
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Chapter 14 Configuring Resilient Ethernet Protocol
Understanding Resilient Ethernet Protocol
Figure 14-1 REP Open Segments
The segment shown in Figure 14-1 is an open segment; there is no connectivity between the two edge
ports. The REP segment cannot cause a bridging loop, and you can safely 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 host
cannot access its usual gateway because of a failure, REP unblocks all ports to ensure that connectivity
is available through the other gateway.
The segment shown in Figure 14-2, with both edge ports located on the same switch, is a ring segment.
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 14-2 REP Ring Segment
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.
E2E1 E2E1
E1
Edge port
Blocked port
Link failure
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E2E1
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