FORE Systems ES-2810 Ethernet Switch User’s Manual
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Concepts in Switching
Concepts in Switching
A.7.2.7 Spanning Tree Topology
The cost factor is used to calculate the distance from each port of a switch to the Root Switch.
On the basis of this, each port on a switch is assigned one of the following states:
Root Port
The port that is closest to the Root Switch. Only one port
on each switch is assigned as the Root Port.
Designated Port The ports that connect to switches further away from
the Root Switch than the switch. The Root Switch
only has Designated Ports.
Blocking If any ports are not assigned a Root Port or a
Designated Port State, they are assigned a
“Blocking” State. Frames (with the exception of
Configuration BPDUs) are not accepted or
transmitted by the port when it is in the Blocking
State. The port can be said to be in stand-by.
A.7.2.8 Frame Propagation
By enforcing this strict hierarchy and by only forwarding frames between Root Ports and Des-
ignated Ports, the possibility of bridging loops is removed.
Frames cannot be sent directly between switches (except via the Root Switch).
A.7.2.9 7-hop Limit
In addition to the strict bridging hierarchy imposed by the Spanning Tree Algorithm, a 7-hop
limit is introduced. Frames should not pass more than 7 bridges and this limits the size of the
bridged network.
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