Cisco Systems A9014CFD manual 12-3, No-neighbor Topology

Chapter 12 Configuring Resilient Ethernet Protocol

Understanding Resilient Ethernet Protocol (REP)

•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.

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 Figure 12-3. In this case, 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 12-3 No-neighbor Topology

E1

REP not

supported

E1 and E2 are configured as edge no-neighbor ports

E2

REP ports

Restrictions

273792

•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.

	Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
OL-23826-09		12-3