Chapter 3: Advanced STP Tuning

Question 1

Configure the STP priority for a switch so that is it is a root bridge or a backup root bridge

Answer 1

spanning-tree vlan “vlan-id” root {primary | secondary} [diameter “diameter”]

or

spanning-tree vlan “vlan id” priority “priority”

Question 2

Configure the STP port cost

Answer 2

spanning-tree [vlan “vlan id”] cost “cost”

Question 3

Configure the STP port priority on the downstream port

Answer 3

spanning-tree [vlan “vlan id”] port-priority “priority”

Question 4

Enable root guard on an interface

Answer 4

spanning-tree guard root

Question 5

Enable STP portfast globally, for a specific port or for a trunk port

Answer 5

spanning-tree portfast default

OR

spanning-tree portfast

OR

spanning-tree portfast trunk

Question 6

Enable BPDU guard globally or for a specific interface

Answer 6

spanning-tree portfast bpduguard default

OR

spanning-tree bpduguard {enable | disable}

Question 7

Enable STP loop guard globally or for a specific interface

Answer 7

spanning-tree loopguard default

OR

spanning-tree guard loop

Question 8

Enable automatic error recovery for BPDU guard

Answer 8

errdisable recovery cause bpduguard

Question 9

Change the automatic error recovery time

Answer 9

errdisable recovery interval “time-seconds”

Question 10

Enable UDLD globally or for a specific port

Answer 10

udld enable {aggressive}

OR

UDLD port {aggressive}

Question 11

Display the list of STP ports in an inconsistent state

Answer 11

show spanning-tree inconsistentports

Question 12

Display the list of neighbor devices running UDLD

Answer 12

show udld neighbors