Rockwell Automation Publication 1783-UM007G-EN-P - February 2017 327
Configure Switch Features Chapter 7
REP Ring Segment
The segment that is shown in Figure 44, with both edge ports 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.
In the following figure, E1 or E2 can be configured as the primary edge port.
Figure 44 - Ring Segment Example
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 support ongoing
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.
Access Ring Topologies
In access ring topologies, the neighboring switch cannot support REP, as
shown in
Figure 45. 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. 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.
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