Downloads |
Table Of Contents
IOS STP Enhancement
Feature Summary
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.
Benefits
The IOS STP Enhancement provides the following benefits:
•
More than one byte on a port number to distinguish interfaces.
•
•
Restrictions
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.
Platforms
This feature is supported on these platforms:
•
•
•
•
•
•
Supported MIBs and RFCs
None.
Configuration Tasks
There are no new configuration tasks.
Configuration Examples
The following example shows the help interface for using the bridge-group priority command:
Router(config)# bridge 1 protocol ieeeRouter(config)# int e0Router(config-if)#bridge-group 1Router(config-if)# bridge-group 1 priority ?<0-255> increments of 2 for IEEE or vlan-bridge, others 1Router(config-if)# bridge-group 1 priority 1Priority in increments of 2 is requiredRouter(config-if)# bridge-group 1 priority 3Priority in increments of 2 is requiredRouter(config-if)# bridge-group 1 priority 2Router(config-if)#Command Reference
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 priority
Use the bridge-group priority interface configuration command to set an interface priority. The interface priority is used to select the designated port for this bridge-group on the connected media. One designated port on each media is needed to compute the spanning tree.
bridge-group bridge-group priority number
Syntax Description
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.
Command Mode
Interface configuration
Usage Guidelines
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.
Examples
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 1The 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 1Related Commands
bridge-group
bridge prioritybridge protocol
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}
no bridge bridge-group protocol {ieee | dec | vlan-bridge}Syntax Description
Default
No Spanning-Tree Protocol is defined.
Command Mode
Global configuration
Usage Guidelines
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.
Note
Example
The following example shows bridge 1 as using the VLAN Bridge Spanning Tree Protocol:
bridge 1 protocol vlan-bridgeRelated Commands
bridge domain
bridge-groupshow spanning-tree
To display information regarding which spanning-tree protocol is running, use the show spanning-tree configuration command.
show spanning tree bridge-group
Syntax Description
bridge-group
Bridge group number, in the range of 1 to 256, specified in the bridge protocol command.
Command Mode
EXEC
Usage Guidelines
This command first appeared in Cisco IOS Release 12.0(1)T
Example
The following example shows that Bridge group 1 is running the VLAN Bridge Spanning Tree protocol.
Router# sh spanning-tree 1Bridge group 1 is executing the VLAN Bridge compatible Spanning Tree protocolBridge Identifier has priority 32768, address 0000.0c37.b055Configured hello time 2, max age 30, forward delay 20We are the root of the spanning treePort Number size is 10 bitsTopology change flag not set, detected flag not setTimes: hold 1, topology change 35, notification 2hello 2, max age 30, forward delay 20Timers: hello 0, topology change 0, notification 0bridge aging time 300Port 8 (Ethernet1) of Bridge group 1 is forwardingPort path cost 100, Port priority 128Designated root has priority 32768, address 0000.0c37.b055Designated bridge has priority 32768, address 0000.0c37.b055Designated port is 8, path cost 0Timers: message age 0, forward delay 0, hold 0BPDU: sent 184, received 0
