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28
To avoid those hazardous situations, follow the recommendations in section
"Spanning Tree Configuration for Fast Ethernet" below.
LAN segment 4
Frame generated from
Station A is still passed
to station B
Figure 10. Preventing Frame Looping
Spanning Tree Configuration for Fast Ethernet
Running the IEEE Spanning Tree Protocol (STP) will create a single spanning tree
covering the entire network. Depending on the topology and configured path costs,
there will be one or more forwarding links between the two clouds.
If there are multiple Fast Ethernet links in multiple switches, the path costs on these
links should be selected such that only one forwards. This will prevent ARE
duplication and the looping problem.
Normally this can be achieved by assigning very large path costs on both sides of
the Fast Ethernet links such that at most one can be forwarding. The Fast Ethernet
ports provides support for STP cost manipulation which does not require cost
configuration on both sides of the link.
For each CRF of Fast Ethernet ports connected to the same Ethernet cloud, a
connection attribute can be assigned (see "TS Connection" on page 56):
•
Primary connection – for a main connection to the Ethernet cloud (default
value for each CRF). This connection is always forwarding if active.
•
Secondary 1 – for a backup connection to the Ethernet cloud. This connection
is always blocking if the primary is active.
CrossFire 8730 Switch Reference Guide, DOC-7047 v. 1.1
Ethernet cloud broken into two
separate clouds.
Station A
Redundant
connections
to Ethernet
CrossFire 8730 - Link 1
Forwarding
Ring 1
Token-Ring
cloud
The direct connection between
station A and B is broken.
X
CrossFire 8730 - Link 2
Forwarding
Ring 2
Bridge 1
Station B
LAN segment 3
Switch Overview
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