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250 Rockwell Automation Publication 1783-UM007I-EN-P - December 2017
Chapter 3 Configure Switch Features
REP and STP can coexist on the same switch, but not on the same port. REP
does not interact with STP. For example, if a port is configured as an REP port,
STP is disabled on that port. STP bridge protocol data units (BPDUs) are not
accepted on or sent from REP ports. However, adjacent REP and STP rings or
domains can share a common link. This common link can be used for passing
REP and STP date plane traffic, or for the STP control plane traffic.
Figure 40 shows an example of a segment consisting of six ports that are spread
across four switches. Ports E1 and E2 are configured as edge ports. When all
ports are operational (as in the segment on the left), one port is blocked, shown
by the diagonal line. When there is a failure in the network, as shown in the
diagram on the right, the blocked port returns to the forwarding state to
minimize network disruption.
REP Open Segment
The segment that is shown in Figure 40 is an open segment. There is no
connectivity between the two edge ports. The REP segment cannot cause a
bridging loop and you can connect the segment edges to any network. All hosts
that are connected to switches inside the segment have two possible
connections to the rest of the network through the edge ports. However, 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 make sure that connectivity
is available through the other gateway.
In the following example, E1 or E2 can be configured as the primary edge port.
Figure 40 - Open Segment Example
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Edge Port
Blocked Port
Link Failure
E1 E1 E2
E2
E1