Administrator Guide

Layer 2 Switching Commands 784
Direct Link Rapid Convergence on STP-PV switches. This command assists
in accelerating spanning-tree convergence after switchover to an alternate
port.
Use the no form of the command to return the configured rate to the default
value (or disable uplinkfast on STP-PV configured switches).
Syntax
spanning-tree uplinkfast [max-update-rate packets/s ]
no spanning-tree uplinkfast [max-update-rate]
• max-update-rate —The rate at which update packets are sent. (Range: 0-
32000)
Default Configuration
The default rate is 150.
Command Modes
Global Configuration Mode
User Guidelines
DirectLink Rapid Convergence (DRC) can be configured even if the switch is
configured for MST(RSTP) mode. It only has an effect when the switch is
configured for STP-PV or RSTP-PV modes. Enabling DRC sets the switch
priority to 49152. Path costs have an additional 3000 added when DRC is
enabled. This reduces the probability that the switch will become the root
switch.
DRC immediately changes to an alternate root port on detecting a root port
failure and change the new root port directly to the fowarding state. A TCN is
sent for this event.
After a switchover to an alternate port (new root port), DRC multicasts a
gratuitous frame on the new root port on behalf of each attached machine so
that the rest of the network knows to use the secondary link to reach that
machine.
DRC is disabled when the administrator modifies the spanning-tree priority
of a VLAN and is re-enabled only when the default priority is restored.
2CSNXXX_SWUM204.book Page 784 Monday, January 25, 2016 1:25 PM