ccnp sw ch 8

  1. Where should the root bridge be placed?

  2. Which of the following is a result of a poorly placed root bridge in a network?

  3. Which of these parameters should you change to make a switch become a root bridge?

  4. What is the default 802.1D STP bridge priority on a Catalyst switch?

  5. Which of the following commands is most likely to make a switch become the root port bridge for vlan 5, assuming that all switches have the default STP parameter?

  6. What is the default path cost of a Gigabit Ethernet switch port?

  7. What command can change the path cost of interface GI 3/1 to a value of 8?

  8. What happens if the root bridge switch and another switch are configured with different STP Hello timer values?

  9. What network diameter value is the basis for the default STP timer calculations?

  10. Where should the STP PortFast feature be used?

  11. Where should the STP UplinkFast feature be enabled?

  12. If used, the STP BackboneFast feature should be enabled on which of these?

  13. Which one of the following connamds can be used to verify the current root bridge in VLAN 10?

  14. What are 2 things to consider when configuring STP root bridge?
    a. configure one switch as root bridge in a determined fashion. (pick the best choice, using placement and/or speed)

    b. configure another switch as a secondary root bridge, in case the primary fails.
  15. What command allows you to set STP bridge priority for vlan 5?
    spanning-tree vlan 5 priority 4096

    Note: STP defaults Bridge ID to 32,768, but you can manually set the ID in increments of 4096.
  16. what command is a macro that forces a switch to become either the pri or sec root bridge?
    spanning-tree vlan 5 root (pri | sec) (diameter 5)

    Note:  Diameter is the number of switches when counting out from the root switch.  This drives the fwd delay and max-age timers for STP.
  17. How do you verify the STP bridge priorities for vlan 5?
    sh spanning-tree vlan 5
  18. What is unique on systems that use the extended system ID?
    the bridge pri is the configured pri number used plus the vlan #. 

    • example:
    • span-tree vlan 100 pri 0

    would show a bridge pri of 100
  19. What command allows you to tune a switchport's path cost?
    from INT cmd:

    span=tree vlan 10 cost 2
  20. What cmd allows you to tune the switchport ID?
    from INT cmd:

    span-tree vlan 10 port-priority 64

    view: show span-tree int gi 3/16
  21. What is the sequence of the four criteria STP uses to choose a path?
    • 1. Lowest Bridge ID
    • 2. Lowest root path cost
    • 3. Lowest sender bridge ID
    • 4. Lowest sender port
  22. What command allows you to manually modify the STP timers?
    • span-tree vlan 5 hello-time (secs)
    • span-tree vlan 5 forward-time (secs)
    • span-tree vlan 5 max-age (secs)

    if you leave out the (vlan id) parameter, it modifies all vlan STP timers
  23. what are 3 methods to allow faster STP convergence if a link fails?


  24. describe portfast.
    It is where the link comes up immediately and allows the PC or VOIP phone to start using it. 

    Use only where the end device is not a switch or router.

    STP is still watching the BPDUs, and will put port into blocking state if a switch is detected.

    can either be global or by interface

    • G  spanning-tree portfast default 
    • I  spanning-tree portfast
  25. describe uplinkfast.
  26. What cmd is a macro that does the following?

    a. sets switchport to access
    b. enables STP portfast
    c. disables PAgP
    • int fa 0/1   (or use int range)
    •     switchport host
  27. Describe uplinkfast
    enables leaf-node switches to have a root port while keeping one or more ports in blocking mode.  If the pri port fails, another blocked port can take over.
  28. Is Uplinkfast per port or for the whole switch?

    what command enables uplinkfast?
    Global.  (entire switch).

    spanning-tree uplinkfast [max-update-rate 100]

    max-update-data is how to control the dummy multicast frames sent.  Def is 150.

    First, make bridge ID 49,152 so it never becomes root.
  29. what mechanism is used to let upstream switches know that a new port is active when using UpLinkFast?

    What cmd verifies Uplinkfast parameters?
    Dummy multicast frames are sent to 0100.0ccd.cdcd  

    The switch sends these dummy frames with the MAC addresses in its cam table.  This multicast is what is controlled by the max-update-rate command . 

    show spanning-tree uplinkfast
  30. What does Backbonefast do?
    It starts to find alternate paths to the root bridge when it receives inferior BPDU from a switch.  This means that the switch has lost its connection (indirect link failure). 

    This process shortens the max age timer so you can save max of 20 seconds. 

    Sw must still go through listening and learning stages.
  31. What are the commands to verify spanning-tree?
    • show spanning-tree
    • show spanning-tree detail
    • show spanning-tree vlan 5 summary
    • show spanning-tree vlan 5 root
    • show spanning-tree vlan 5 bridge
    • show spanning-tree int gi 0/1
    • show spanning-tree uplinkfast
    • show spanning-tree backbonefast
Card Set
ccnp sw ch 8
ch 8