Configuring Uplinkfast; Enabling Uplinkfast - Cisco WS-C4003 - Catalyst 4000 Chassis Switch Software Configuration Manual

Chapter 8 Configuring Spanning Tree PortFast, UplinkFast, and BackboneFast, and Loop Guard
As soon as the switch transitions the alternate port to the forwarding state, the switch begins transmitting
dummy multicast frames on that port, one for each entry in the local EARL table (except those entries
associated with the failed root port). By default, approximately 15 dummy multicast frames are
transmitted per 100 milliseconds.
Each dummy multicast frame uses the station address in the EARL table entry as its source MAC address
and a dummy multicast address (01-00-0C-CD-CD-CD) as the destination MAC address.
Switches receiving these dummy multicast frames immediately update their EARL table entries for each
source MAC address to use the new port, allowing the switches to begin using the new path almost
immediately.
If connectivity on the original root port is restored, the switch waits for a period equal to twice the
forward delay time plus 5 seconds before transitioning the port to the forwarding state in order to allow
the neighbor port time to transition through the listening and learning states to the forwarding state.

Configuring UplinkFast

These sections describe how to configure the UplinkFast feature on the switch:
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Enabling UplinkFast

When you enable UplinkFast on the switch, UplinkFast processing is enabled and the spanning tree
bridge priority for all VLANs is set to 49152, making it unlikely that the switch will become the root
switch. In addition, the spanning tree port cost and port-VLAN cost of all ports on the switch is increased
by 3000.
The station_update_rate value in the UplinkFast command represents the number of dummy multicast
packets transmitted per 100 milliseconds (the default is 15 packets per 100 milliseconds) in the event of
a direct link failure.
Use the all-protocols on keywords on switches that have UplinkFast enabled but do not have protocol
filtering enabled, and that are connected to upstream switches in the network that have protocol filtering
enabled. The all-protocols on keywords cause the switch to generate multicasts for each
protocol-filtering group.
On switches with both UplinkFast and protocol filtering enabled, or if no other switches have protocol
filtering enabled, you do not need to use the all-protocols on keywords.
Note When you enable UplinkFast, it affects all VLANs on the switch. You cannot configure UplinkFast on a
per-VLAN basis.
To enable UplinkFast, perform this task in privileged mode:
Task
Step 1
Enable UplinkFast on the switch.
Step 2
Verify that UplinkFast is enabled.
78-12647-02
Enabling UplinkFast, page 8-9
Disabling UplinkFast, page 8-10
Software Configuration Guide—Catalyst 4000 Family, Catalyst 2948G, Catalyst 2980G, Releases 6.3 and 6.4
Command
set spantree uplinkfast enable [rate
station_update_rate] [all-protocols {off | on}]
show spantree uplinkfast [vlans]
Configuring UplinkFast
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