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Rockwell Automation Publication 1783-UM007I-EN-P - December 2017 249
Configure Switch Features Chapter 3
Resilient Ethernet Protocol
(REP) REP provides an alternative to Spanning Tree Protocol (STP) to control
network rings and loops, handle link failures, and improve convergence time.
REP controls a group of ports that are connected in a segment, makes sure that
the segment does not create any bridging loops, and responds to link failures
within the segment. REP provides a basis for constructing more complex
networks and supports VLAN load balancing.
REP is a segment protocol. One REP segment is a chain of ports that are
connected to each other and configured with a segment ID. Each segment
consists of standard (transit) segment ports and two user-configured edge
ports. A switch can have no more than two ports that belong to the same
segment, and each segment port can have only one external neighbor. A
segment can go through a shared medium; however, on any link, only two
ports can belong to the same segment. REP is supported only on Layer 2 trunk
interfaces. Selecting the Switch for Automation Smartport enables Layer 2
trunking. REP is supported on EtherChannels, but not on an individual port
that belongs to an EtherChannel.
You can construct almost any type of network that is based on REP segments.
REP also supports VLAN load-balancing, controlled by the primary edge port
but occurring at any port in the segment.
These types of REP ports are selectable in Device Manager:
•
Primary—This port is a primary edge port. This port always participates
in VLAN load balancing in the REP segment.
•
Edge—This port is a secondary edge port. It also participates in VLAN
load balancing in the REP segment.
Edge ports are termination points of an REP segment. You must
configure two edge ports, including one primary edge port, for each
REP segment. Entering edge without primary configures the port as a
secondary edge port. Primary and secondary edge ports must be
configured even if support of VLAN balancing is not required.
•
Transit—This port is a non-edge port in the REP segment.
•
No-Neighbor Primary—This port is a primary edge port connected a
non-REP switch.
•
No-Neighbor—This port is a secondary edge port that is connected to a
non-REP switch.
The no-neighbor edge ports contain all properties of regular edge ports.
These ports enable the construction of a REP ring containing a switch
that does not support REP protocol.
•
None—This port is not part of the REP segment.