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Alteon OS Application Guide
116
Chapter 5: Spanning Tree Group 42C4911, January 2007
Fast Uplink Convergence
Fast Uplink Convergence enables the GbESM to quickly recover from the failure of the pri-
mary link or trunk group in a Layer 2 network using Spanning Tree Protocol. Normal recovery
can take as long as 50 seconds, while the backup link transitions from Blocking to Listening to
Learning and then Forwarding states. With Fast Uplink Convergence enabled, the GbESM
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, Alteon OS automatically makes the following
configuration changes:
Sets the bridge priority to 65535 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 GbESM to get to another
switch unless there is no other path.
These changes are reversed if the feature is disabled.
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)