3Com 3C13636 Configuration Manual page 357

3Com Router 3000 Ethernet Family
Configuration Guide
Max Age of BPDU
Hello Time of BPDU
Forward Delay of port state transition
I. Spanning tree protocol algorithm
The spanning tree protocol algorithm contains enough information for a bridge to
perform the following tasks:
Specify the root bridge. The bridge with the smallest Bridge Identifier will be the root
bridge of the local network.
Specify the designated bridge. Designated bridge is the one directly connected with
the current (subordinate) bridge and responsible for forwarding data to the current
(subordinate) bridge. The path cost via a designated bridge is the lowest between the
leaf nodes and root bridge.
Specify the designated port. Designated ports are those on the designated bridge and
responsible for forwarding data to the subordinate bridges. The path cost of BPDUs
sent on a designated port will be the lowest.
Specify the root port. Root port refers to the one on the current bridge and responsible
for receiving the data forwarded by the designated bridge.
Specify blocked ports. Except the designated ports and the root ports, all other ports
will be blocked and are called blocked ports.
Upon the computation of the minimum spanning tree, the newly generated root port
and designated ports begin to forward packets after a period of forward delay. After all
the bridges on the network accomplish the spanning tree computation, the network
topology will be stabilized and will remain the same until the network takes changes.
The following figure illustrates the topology of the minimum spanning tree on a
network:
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3-8
Chapter 3 Bridge Configuration