Datasheet

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To provide path redundancy, STP defines a tree that spans all switches in an extended network. STP forces certain redundant
data paths into a standby (blocked) state. If one network segment in the STP becomes unreachable, or if STP costs change, the
spanning-tree algorithm reconfigures the spanning-tree topology and reestablishes the link by activating the standby path as shown
in Figure 2-1.
Figure 2-1 Spanning Tree Convergence
In addition to the enhancements Cisco has made to the Spanning Tree Protocol (PortFast, UplinkFast, BackboneFast), the Catalyst
6000 and 6500 Series switches now have the ability to enable or disable STP on a per-VLAN basis. Previous to this, STP had to be
either enabled or disabled on the entire switch. This enhancement allows the administrator to better define where the Spanning Tree
Protocol should operate in the network. For example, VLANs that are architected without the possibility of multiple redundant
links (that is, loop) might have improved stability when STP is disabled.
Note that STP is enabled by default on all VLANs and on all newly created VLANs.
Useful References
• Catalyst 6000 Family Overview
http://cco/warp/public/cc/cisco/mkt/switch/cat/6000/index.shtml
• Catalyst 6000 Family Documentation
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/index.htm
• Catalyst 6000 Multilayer Switching Module
http://cco/warp/public/cc/cisco/mkt/switch/cat/6000/prodlit/c60fm_ds.htm
• Catalyst 6000 Family Release Notes
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/relnotes/index.htm
System Requirements for 5.1CSX
• Release 5.1CSX software runs on all Cisco Catalyst 6000 Family Supervisors.
System Requirements for 5.2CSX
• Release 5.2CSX software runs on all Cisco Catalyst 6000 Family Supervisors.
STP Root
STP
Blocked
for Red
Normal
Forwarding
Link
X
STP Root
Path Becomes Alive
Link
Failure
RLQ
Inquiry and
Response