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ccnp sw ch 9

  1. Why is it important to protect the placement of the root bridge?




    C.
  2. Which of the following freatures protects a switch port from accepting superior BPDUs?




    C.
  3. Which of the following commands canyou use to enable STP ROot guard on a switch port?




    C.
  4. Where should the STP Root Guard feature be enabled on a switch?




    D.
  5. Which of the following features protects a switch port from accepting BPDUs when PortFast is enabled?




    A.
  6. To maintain a loop-free STP topology, which one of the following should a switch up-link be protected against?




    A.
  7. Which of the following commands can enable STP Loop Guard on a switch port?




    D.
  8. STP Loop Guard detects which of the following conditions?




    C.
  9. Which of the following features can actively test for the loss of the receive side of a link between switches?




    B.
  10. UDLD must detect a unidirectional link before which of the following?




    C.
  11. What must a switch do when it receives a UDLD message on a link?




    D.
  12. Which of the following features effectively disables spanning-tree operation on a switch port?




    A.
  13. To reset switch ports that have been put into the errdisable mode by UDLD, which one of the following commands should be used?




    A.
  14. T/F  You should use BPDU guard on all switch ports where STP PortFast is enabled?
    T
  15. What two commands protect against sudden loss of BPDUs on a port?
    Loop Guard and UDLD 

    UDLD = Unidirectional Link Detection
  16. Is BPDU Guard enabled or disabled by default?
    Disabled. 

    It can be enabled either globally or by interface.

    • G  spanning-tree portfast bpduguard default
    • I  spanning-tree bpduguard enable
  17. Explain root guard.
    It protects a portfast port from receiving BPDUs.  It can only forward or relay BPDUs.

    This prevents a rogue switch from being connected with a superior Root bridge ID and taking over the STP process.
  18. What does Loop Guard do?
    Situation:  port that is in blocking state, and receiving BPDUs.  BPDUs stop, Max-age timer expires, then the port will transitions through STP process.  

    It prevents a port opening that loses BPDUs. Loop Guard puts port in a loop-inconsistent state until BPDUs are received again.

    Use Loop Guard only if you NEVER want the port to be either root port or designated port.  It should be used on all non-designated ports.
  19. Can you have root guard and loop guard active on the same port?
    No.  if you enable loop guard, it will disable root guard.
  20. What is UDLD used for?
    When a PT to PT link loses some of its functionality, and is sending traffic in only direction.  Usually physical.  

    Must be set up on both switches. Uses echo process to keep track of neighbors.   

    2 modes.  normal and aggressive.  

    Normal.  UDLD detects, then a message is sent.  port is still up. 

    Aggressive.  UDLD messages are sent once per second x8. then port is put in err-disabled state ans msg is sent.  

    UDLD is config on a per port basis or globally for fiber optic.
  21. State cmd for setting up UDLD.
    G  udld {enable | aggressive | message time 15}

    I  udld {enable | aggressive |disable}
  22. Describe BPDU filtering.
    This is where you can filter all BPDU traffic on a port.  

    Can be either Global or per INT.

    • G  spanning-tree portfast bpdufilter default
    • I  spanning-tree bpdufilter {enable | disable}

    Note:  default above puts bpdu filtering on for all ports that have portfast enabled.  if portfast is disabled on an INT, then BPDU filtering will NOT be enabled.
Author
boultonm
ID
236102
Card Set
ccnp sw ch 9
Description
ch 9
Updated

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