Extreme Networks ExtremeWare XOS Guide Manual page 156

Spanning Tree Protocol (STP)
2 Bridge E believes that bridge A is the root bridge. When bridge E receives the BPDU on its root port
from bridge F, bridge E:
• Determines that it received an inferior BPDU
• Immediately begins the max age timer on its root port
• Performs a configuration update
After the configuration update, bridge E:
• Regards itself as the new root bridge
• Sends BPDU messages on both of its designated ports to bridges F and D, respectively
Figure 18: New root bridge selected
A
A , 0
F
F , 0
3 When bridge F receives the superior BPDU and configuration update from bridge E, bridge F:
• Decides that the receiving port is the root port
• Determines that bridge E is the root bridge
Figure 19: Communicating new root bridge status to neighbors
A
A , 0
F
E , 1
156
B C
A , 1 A , 2
Designated
port
E D
E , 0 A , 3
BPDU
B C
A , 1 A , 2
Designated
port
E D
E , 0 A , 3
Root
port
EX_055c
Root
port
EX_055d
ExtremeWare XOS 10.1 Concepts Guide