18-5
Catalyst 2975 Switch Software Configuration Guide
OL-19720-02
Chapter 18 Configuring Optional Spanning-Tree Features
Understanding Optional Spanning-Tree Features
Figure 18-3
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, as shown in
approximately 1 to 5 seconds.
Figure 18-4
UplinkFast Example After Direct Link Failure
Understanding Cross-Stack UplinkFast
For Catalyst 2975 switches, the UplinkFast feature is the cross-stack UplinkFast feature. 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 of connectivity to the backbone. With this feature, you can have a redundant
and resilient network in some configurations. CSUF is automatically enabled when you enable the
UplinkFast feature by using the
spanning-tree uplinkfast
global configuration command.
CSUF might not provide a fast transition all the time; in these cases, the normal spanning-tree transition
occurs, completing in 30 to 40 seconds. For more information, see the
Convergence” section on page 18-7
L1
L2
L3
Switch C
Switch A
(Root)
Switch B
Blocked port
43575
L1
L2
L3
Switch C
Switch A
(Root)
Switch B
UplinkFast transitions port
directly to forwarding state.
Link failure
43576
Содержание 2975 - Catalyst LAN Base Switch
Страница 36: ...Contents xxxvi Catalyst 2975 Switch Software Configuration Guide OL 19720 02 ...
Страница 40: ...xxxviii Catalyst 2975 Switch Software Configuration Guide OL 19720 02 Preface ...
Страница 62: ...1 22 Catalyst 2975 Switch Software Configuration Guide OL 19720 02 Chapter 1 Overview Where to Go Next ...
Страница 398: ...13 30 Catalyst 2975 Switch Software Configuration Guide OL 19720 02 Chapter 13 Configuring VLANs Configuring VMPS ...
Страница 424: ...15 18 Catalyst 2975 Switch Software Configuration Guide OL 19720 02 Chapter 15 Configuring VTP Monitoring VTP ...
Страница 628: ...26 8 Catalyst 2975 Switch Software Configuration Guide OL 19720 02 Chapter 26 Configuring UDLD Displaying UDLD Status ...
Страница 660: ...28 8 Catalyst 2975 Switch Software Configuration Guide OL 19720 02 Chapter 28 Configuring RMON Displaying RMON Status ...
Страница 888: ...38 32 Catalyst 2975 Switch Software Configuration Guide OL 19720 02 Chapter 38 Troubleshooting Troubleshooting Tables ...