Brocade Multi-Service IronWare Switching Configuration Guide (Supporting R05.6.00) - Manual (Page 438)

408 Multi-Service IronWare Switching Configuration Guide
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Edge ports and Edge port roles
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Ports on Switch 1
All ports on Switch 1, the root bridge, are assigned Designated port roles.
Ports on Switch 2
Port2 on Switch 2 directly connects to the root bridge; therefore, Port2 is the Root port.
Switch 2’s bridge priority value is superior to that of Switch 3 and Switch 4; therefore, the ports on
Switch 2 that connect to Switch 3 and Switch 4 are given the Designated port role.
Furthermore, Port7 and Port8 on Switch 2 are physically connected. The RST BPDUs transmitted by
Port7 are superior to those Port8 transmits. Therefore, Switch 2 is the Backup port and Port7 is the
Designated port.
Ports on Switch 3
Port2 on Switch 3 directly connects to the Designated port on the root bridge; therefore, it assumes
the Root port role.
The root path cost of the RST BPDUs received on Port4/Switch 3 is inferior to the RST BPDUs
transmitted by the port; therefore, Port4/Switch 3 becomes the Designated port.
Similarly, Switch 3 has a bridge priority value inferior to Switch 2. Port3 on Switch 3 connects to
Port 3 on Switch 2. This port will be given the Alternate port role, since a Root port is already
established on this bridge.
Ports Switch 4
Switch 4 is not directly connected to the root bridge. It has two ports with superior incoming RST
BPDUs from two separate LANs: Port3 and Port4. The RST BPDUs received on Port3 are superior to
the RST BPDUs received on port 4; therefore, Port3 becomes the Root port and Port4 becomes the
Alternate port.
Edge ports and Edge port roles
Brocade’s implementation of RSTP allows ports that are configured as Edge ports to be present in
an RSTP topology. (
Figure 73 ). Edge ports are ports of a bridge that connect to workstations or
computers. Edge ports do not register any incoming BPDU activities.
Edge ports assume Designated port roles. Port flapping does not cause any topology change
events on Edge ports since RSTP does not consider Edge ports in the spanning tree calculations.