Cisco Catalyst 2960 Series, Configuration Manual

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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 22: 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 23: UplinkFast Example After Direct Link Failure
Related Topics
Specifying the MST Region Configuration and Enabling MSTP , on page 261
MSTP Configuration Guidelines, on page 243
Multiple Spanning-Tree Regions, on page 245
Enabling UplinkFast for Use with Redundant Links , on page 307
Events That Cause Fast Convergence, on page 294
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
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
291
Information About Optional Spanning-Tree Features