ccnp sw ch 9

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Author:
boultonm
ID:
236102
Filename:
ccnp sw ch 9
Updated:
2013-10-01 04:57:00
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ccnp
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ch 9
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  1. Why is it important to protect the placement of the root bridge?

    a. To keep two root bridges from becoming active
    b. To keep the STP topology stable
    c. So al hosts have the correct gateway
    d. So the root bridge can have complete knowledge of the STP topology
    b
  2. Which of the following freatures protects a switch port from accepting superior BPDUs?

    a. STP Loop guard
    b. STP BPDU guard
    c. STP Root guard
    d. UDLD
    c
  3. Which of the following commands canyou use to enable STP ROot guard on a switch port?

    a. spanning-tree root guard
    b. spanning-tree root-guard
    c. spanning-tree guard root
    d. spanning-tree rootguard enable
    c
  4. Where should the STP Root Guard feature be enabled on a switch?

    a. All ports
    b. Only ports where the root bridge should never appear
    c. Only ports where the root bridge should be located
    d. Only ports with PortFast enabled
    b
  5. Which of the following features protects a switch port from accepting BPDUs when PortFast is enabled?

    a. STP Loop guard
    b. STP BPDU guard
    c. STP Root guard
    d. UDLD
    b
  6. To maintain a loop-free STP topology, which one of the following should a switch up-link be protected against?

    a. A sudden loss of BPDUs
    b. Too many BPDUs
    c. The wrong version of BPDUs
    d. BPDUs relayed from the root bridge
    a
  7. Which of the following commands can enable STP Loop Guard on a switch port?

    a. spanning-tree root guard
    b. spanning-tree root-guard
    c. spanning-tree guard root
    d. spanning-tree rootguard enable
    b
  8. STP Loop Guard detects which of the following conditions?

    a. The sudden appearance of superior BPDUs
    b. The sudden lack of BPDUs
    c. The appearance of duplicate BPDUs
    d. The appearance of two root bridges
    b
  9. Which of the following features can actively test for the loss of the receive side of a link between switches?

    a. POST
    b. BPDU
    c. UDLD
    d. STP
    c
  10. UDLD must detect a unidirectional link before which of the following?

    a. The Max Age timer expires
    b. STP moves the link to the Blocking state
    c. STP moves the link to the Forwarding state
    d. STP moves the link to the Listening state
    c
  11. What must a switch do when it receives a UDLD message on a link?

    a. Relay the message on to other switches
    b. Send a UDLD ack
    c. Echo the message back across the link
    d. Drop the message
    c
  12. Which of the following features effectively disables spanning-tree operation on a switch port?

    a. STP PortFast
    b. STP BPDU filtering
    c. STP BPDU Guard
    d. STP Root Guard
    b
  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. clear errdisable udld
    b. udld reset
    c. no udld
    d. show udld errdisable
    b
  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.

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