Configuring Spanning Tree

Configuring Spanning Tree
The configuration of spanning tree is pretty simple unless you want to change your timers or
add multiple spanning tree instances—then it can get complex. The timers and more advanced
configurations are covered in Chapter 16.
STP is enabled on all Cisco switches by default. However, you might want to change your
spanning tree configuration to have many spanning tree instances. This means that each VLAN
can be its own spanning tree. This is known as Per-VLAN spanning tree.
To enable or disable spanning tree on a set-based switch, use the set spantree parameter command.
This is performed on a VLAN-by-VLAN basis rather than a port-by-port configuration:
Terry_4000> (enable) set spantree disable 1-1005
Spantrees 1-1005 disabled.
Terry_4000> (enable) set spantree enable 1-1005
Spantrees 1-1005 enabled.
The preceding configuration shows the disabling of spanning tree on an individual VLAN
basis. To enable spanning tree on an individual VLAN basis, use set spantree enable VLAN(s).
Cisco recommends that you do not disable spanning tree on a switch, particularly on uplinks
where a loop can occur.