Cisco Catalyst 2960-XR Configuration Guide

This topology has no link failures. Switch A, the root switch, is connected directly to Switch B over link L1
and to Switch C over link L2. The Layer 2 interface on Switch C that is connected directly to Switch B is in
a blocking state.
Figure 12: UplinkFast Example Before Direct Link Failure
If Switch C detects a link failure on the currently active link L2 on the root port (a direct link failure), UplinkFast
unblocks the blocked interface on Switch C and transitions it to the forwarding state without going through
the listening and learning states. This change takes approximately 1 to 5 seconds.
Figure 13: UplinkFast Example After Direct Link Failure
Related Topics
Specifying the MST Region Configuration and Enabling MSTP, on page 59
MSTP Configuration Guidelines, on page 44
Multiple Spanning-Tree Regions, on page 45
Enabling UplinkFast for Use with Redundant Links, on page 95
Events That Cause Fast Convergence, on page 86
Cross-Stack UplinkFast
Cross-Stack UplinkFast (CSUF) provides a fast spanning-tree transition (fast convergence in less than 1 second
under normal network conditions) across a switch stack. During the fast transition, an alternate redundant link
on the switch stack is placed in the forwarding state without causing temporary spanning-tree loops or loss
Catalyst 2960-XR Switch Layer 2 Configuration Guide, Cisco IOS Release 15.0(2)EX1
OL-29424-01 83
Configuring Optional Spanning-Tree Features
Cross-Stack UplinkFast

Cisco Catalyst 2960-XR Specifications

General

Stacking Bandwidth	80 Gbps
Layer Support	Layer 2 and Layer 3
Jumbo Frame Support	9198 bytes
RAM	512 MB
Input Voltage	100-240V AC
Model	Catalyst 2960-XR
Uplink Interfaces	4 x 1G SFP or 2 x 10G SFP+
Downlink Interfaces	24 or 48 x Gigabit Ethernet ports
Power Supply	Internal
MAC Address Table Size	16, 000 entries
PoE	Available on PoE models
Weight	4.5 kg
Features	energy efficiency
Stacking	Up to 8 switches
Operating Temperature	0 to 45°C