NEC INTELLIGENT L2 SWITCH N8406-022A - Manual (Page 55)

Spanning Tree Protocol 55
Configuring Port Fast Forwarding
Use the following CLI commands to enable Port Fast Forwarding on an external port.
>> # /cfg/l2/stp 1/port 20 (Select port 20)
>> Spanning Tree Port 20# fastfwd ena (Enable Port Fast Forwarding)
>> Spanning Tree Port 20# apply (Make your changes active)
>> Spanning Tree Port 20# save (Save for restore after reboot)
Fast Uplink Convergence
Fast Uplink Convergence enables the switch to quickly recover from the failure of the primary link or trunk group in
a Layer 2 network using Spanning Tree Protocol. Normal recovery can take as long as 60 seconds, while the
backup link transitions from Blocking to Listening to Learning and then Forwarding states. With Fast Uplink
Convergence enabled, the switch immediately places the secondary path into Forwarding state, and sends
multicasts of addresses in the forwarding database (FDB) and ARP table over the secondary link so that upstream
switches can learn the new path.
Configuration guidelines
When you enable Fast Uplink Convergence, the switch software automatically makes the following configuration
changes:
•
Increases the bridge priority to 65500 so that it does not become the root switch.
•
Increases the cost of all of the external ports by 3000, across all VLANs and Spanning Tree Groups. This
ensures that traffic never flows through the switch to get to another switch unless there is no other path.
When you disable Fast Uplink Convergence, the bridge priorities and path cost are set to their default values for all
STP groups.
Configuring Fast Uplink Convergence
Use the following CLI commands to enable Fast Uplink Convergence on external ports:
>> # /cfg/l2/upfast ena (Enable Fast Uplink convergence)
>> Layer 2# apply (Make your changes active)
>> Layer 2# save (Save for restore after reboot)