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The IOS Spanning Tree Extension broadens the original implementation with increased port identification capability, improved path cost determination, and support for a new VLAN bridge spanning-tree protocol.
The IOS STP Enhancement provides the following benefits:
Port Number size of the Port ID support is applied only to IEEE and Vlan-Bridge Spanning Tree protocols. The DEC protocol only has 8 bits on the port id, so the extension of the Port ID cannot be applied.
The expansion of the Port Number field into the port priority portion of the Port ID changes the useful values the port priority can be assigned. This expansion is an extension of the 802.1D Spanning Tree Protocol.
The way to calculate the Port Path Cost is only support in IEEE and vlan-bridge Spanning Tree environment.
Vlan-bridge Spanning Tree protocol in this phase will support following medias - ethernet, fast ethernet, FDDI, ATM, serial (hdlc, ppp, frame-relay, frame-relay ietf, smds, x.25). Other medias will be added in future releases.
This feature is supported on these platforms:
None.
There are no new configuration tasks.
The following example shows the help interface for using the bridge-group priority command:
Router(config)# bridge 1 protocol ieee Router(config)# int e0 Router(config-if)#bridge-group 1 Router(config-if)# bridge-group 1 priority ? <0-255> increments of 2 for IEEE or vlan-bridge, others 1 Router(config-if)# bridge-group 1 priority 1 Priority in increments of 2 is required Router(config-if)# bridge-group 1 priority 3 Priority in increments of 2 is required Router(config-if)# bridge-group 1 priority 2 Router(config-if)#
This section documents new or modified commands. All other commands used with this feature are documented in the Cisco IOS Release 12.0 command references.>>
bridge-group | Number of the bridge group to which the interface belongs. It must be a number in the range 1 to 63. |
number | Priority number ranging from 0 to 255. |
Interface configuration
This command first appeared in Cisco IOS Release 10.0.
The lower the number, the more likely it is that the bridge on the interface will be chosen as the root.
The following example shows the bridge-group priority help information for 9-bit port number size:
Router(config-if)# bridge-group 1 priority ? <0-255> increments of 2 for IEEE or vlan-bridge, others 1
The following example shows the bridge-group priority help information for 10-bit port number size:
Router(config-if)# bridge-group 1 priority ? <0-255> increments of 4 for IEEE or vlan-bridge, others 1
bridge-group
bridge priority
Use the bridge protocol global configuration command to define the type of Spanning-Tree Protocol. Use the no form of this command with the appropriate keywords and arguments to delete the bridge group.
bridge bridge-group protocol {ieee | dec | vlan-bridge}
bridge-group | Number in the range 1 to 63 that you choose to refer to a particular set of bridged interfaces. Frames are bridged only among interfaces in the same group. You will use the group number you assign in subsequent bridge configuration commands. |
ieee | |
dec | |
vlan-bridge | VLAN-Bridge Spanning-Tree Protocol. |
No Spanning-Tree Protocol is defined.
Global configuration
This command first appeared in Cisco IOS Release 10.0.
The routers support two Spanning-Tree Protocols: the IEEE 802.1 standard and the earlier Digital Spanning-Tree Protocol upon which the IEEE standard is based. Multiple domains are supported for the IEEE 802.1 Spanning-Tree Protocol.
The following example shows bridge 1 as using the VLAN Bridge Spanning Tree Protocol:
bridge 1 protocol vlan-bridge
bridge domain
bridge-group
To display information regarding which spanning-tree protocol is running, use the show spanning-tree configuration command.
show spanning tree bridge-group
bridge-group | Bridge group number, in the range of 1 to 256, specified in the bridge protocol command. |
EXEC
This command first appeared in Cisco IOS Release 12.0(1)T
The following example shows that Bridge group 1 is running the VLAN Bridge Spanning Tree protocol.
Router# sh spanning-tree 1 Bridge group 1 is executing the VLAN Bridge compatible Spanning Tree protocol Bridge Identifier has priority 32768, address 0000.0c37.b055 Configured hello time 2, max age 30, forward delay 20 We are the root of the spanning tree Port Number size is 10 bits Topology change flag not set, detected flag not set Times: hold 1, topology change 35, notification 2 hello 2, max age 30, forward delay 20 Timers: hello 0, topology change 0, notification 0 bridge aging time 300 Port 8 (Ethernet1) of Bridge group 1 is forwarding Port path cost 100, Port priority 128 Designated root has priority 32768, address 0000.0c37.b055 Designated bridge has priority 32768, address 0000.0c37.b055 Designated port is 8, path cost 0 Timers: message age 0, forward delay 0, hold 0 BPDU: sent 184, received 0
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