Owner's Manual

554 | Chapter 18. STP
NETGEAR 8800 User Manual
Figure 43. Down Link Detected
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.
As shown in Figure 44, 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 44. New Root Bridge Selected
3. As shown in Figure 45, 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.
EX_055b
B
A , 1
C
A , 2
E
A , 2
D
A , 3
BPDU
Down
link
A
A , 0
F
F , 0
Designated
port
Root
port
EX_055c
B
A , 1
C
A , 2
E
E , 0
D
A , 3
BPDU
A
A , 0
F
F , 0
Designated
port
Root
port