INE R&S ATC015 ~ 018 - STP BPDU Filter, BPDU Guard , Root Guard , Loop Guard, Unidirectional Link Detection (UDLD)

Advanced STP Features

• BPDU Filter
– Filter BPDUs in and out
• BPDU Guard
– If BPDU is received shut port down

• Root Guard
– If superior BPDU is received shut port down
• Loop Guard & UDLD
– Prevent unidirectional links

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Global Config                                                            Interface Config

spanning-tree portfast bpdufilter default                   spanning-tree bpdufilter enable
spanning-tree portfast bpduguard default                  spanning-tree bpduguard enable
                                                                                   spanning-tree rootguard
spanning-tree loopguard default                                spanning-tree guard loop

Enabling UDLD Globally

udld {aggressive | enable | message time message-timer-interval}

Specify the UDLD mode of operation:

•aggressive—Enables UDLD in aggressive mode on all fiber-optic ports.

•enable—Enables UDLD in normal mode on all fiber-optic ports on the switch. UDLD is disabled by default.

An individual interface configuration overrides the setting of the udld enable global configuration command.

For more information about aggressive and normal modes, see the "Modes of Operation" section.

•message time message-timer-interval—Configures the period of time between UDLD probe messages on ports that are in the advertisement phase and are detected to be bidirectional. The range is from 1 to 90 seconds.

Note This command affects fiber-optic ports only. Use the udld interface configuration command to enable UDLD on other port types.

Enabling UDLD on an Interface

udld port [aggressive]

UDLD is disabled by default.

•udld port—Enables UDLD in normal mode on the specified port.

•udld port aggressive—Enables UDLD in aggressive mode on the specified port.

 

 

Google: loop guard versus udld

Spanning-Tree Protocol Enhancements using Loop Guard and BPDU Skew Detection Features

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a0080094640.shtml

 

Google: site:blog.ine.com udld loop

UDLD Modes of Operation

http://blog.ine.com/2008/07/05/udld-modes-of-operation/