Specifications

218 ExtremeWare XOS 11.0 Concepts Guide
Spanning Tree Protocol
4 Bridge D believes that bridge A is the root bridge. When bridge D receives the BPDU from bridge E
on its alternate port, bridge D:
• Immediately begins the max age timer on its alternate port.
• Performs a configuration update.
As shown in Figure 28, after the configuration update, bridge D:
• Moves the alternate port to a designated port.
• Sends a “propose” message to bridge E to solicit confirmation of its designated role and to
rapidly move the port into the designated state.
Figure 28: Sending a propose message to confirm a port role
5 Upon receiving the proposal, bridge E (as shown in Figure 29):
• Performs a configuration update.
• Changes its receiving port to a root port.
The existing designated port enters the blocking state.
Bridge E then sends:
• A “propose” message to bridge F.
• An “agree” message from its root port to bridge D.
Figure 29: Communicating port status to neighbors
EX_055e
B
A , 1
C
A , 2
E
E , 0
Propose BPDU
A
A , 0
F
E , 1
D
A , 3
Designated
port
Root
port
EX_055f
B
A , 1
C
A , 2
E
A , 4
Agree BPDU
A
A , 0
F
E , 1
D
A , 3
Designated
port
Root
port