DELL N3000 User Manual

Configuring the Spanning Tree Protocol

on ports that should have a path to the root. The port where the switch 

received the inferior BPDU is excluded because it already failed; self-looped 

and designated ports are eliminated as they do not have a path to the root. 

Upon receiving a negative RLQ response on a port, the port has lost 

connection to the root and the switch ages-out its BPDU. If all other non-

designated ports received a negative answer, the switch has lost the root and 

restarts the STP calculation. 
If the response confirms the switch can still access the root bridge via a 

particular port, it immediately ages-out the port on which the inferior BPDU 

was received. 
If the switch only received responses with a root different from the original 

root, it has lost the root port and restarts the STP calculation immediately. 

Inferior BDPU received. Are there 

other non-self-looped 

non-designated ports?

Connectivity to root is lost. 

Recompute spanning-tree.

No

Yes: Can still reach root on a port.

No

Yes -> Send RLQ query on non-designated ports.

Wait for RLQ responses.

Connectivity to root still exists –

age out port with inferior BPDU. 

Have received response for every 

RLQ sent?

No

Are all RLQ responses negative?

No, end 

processing

Yes

Negative: Root lost on this port

Age-out the BPDU for this port. 

Have received response for 

every RLQ sent?

Yes

No