18-6
Catalyst 2975 Switch Software Configuration Guide
OL-19720-02
Chapter 18 Configuring Optional Spanning-Tree Features
Understanding Optional Spanning-Tree Features
How CSUF Works
CSUF ensures that one link in the stack is elected as the path to the root. As shown in
, the
stack-root port on Switch 1 provides the path to the root of the spanning tree. The alternate stack-root
ports on Switches 2 and 3 can provide an alternate path to the spanning-tree root if the current stack-root
switch fails or if its link to the spanning-tree root fails.
Link 1, the root link, is in the spanning-tree forwarding state. Links 2 and 3 are alternate redundant links
that are in the spanning-tree blocking state. If Switch 1 fails, if its stack-root port fails, or if Link 1 fails,
CSUF selects either the alternate stack-root port on Switch 2 or Switch 3 and puts it into the forwarding
state in less than 1 second.
Figure 18-5
Cross-Stack UplinkFast Topology
When certain link loss or spanning-tree events occur (described in
“Events that Cause Fast Convergence”
), the Fast Uplink Transition Protocol uses the neighbor list to send fast-transition
requests to stack members.
The switch sending the fast-transition request needs to do a fast transition to the forwarding state of a
port that it has chosen as the root port, and it must obtain an acknowledgement from each stack switch
before performing the fast transition.
Switch 1
Spanning-
tree root
Backbone
Catalyst 2975 switch stack
Stack port
connections
250882
Switch 2
Stack port
connections
Forward
Link 1
(Root link)
Link 2
(Alternate
redundant
link)
Link 3
(Alternate
redundant
link)
100 or 1000 Mbps
100 or 1000 Mbps
100 or 1000 Mbps
Forward
Forward
Switch 3 Stack port
connections
Stack-root port
Alternate stack-
root port
Alternate stack-
root port
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 ...