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STP Questions 2

September 11th, 2017 in SWITCH 300-115 Go to comments

Question 1

Explanation

With the use of dot1q (802.1Q) encapsulation, control frames (include STP, CDP, VTP…) are tagged with VLAN 1 if the switch native VLAN is changed -> that means STP BPDU is tagged with VLAN 1 when the native VLAN is set to VLAN 99 -> Answer A is correct.

Reference: http://www.cisco.com/c/en/us/support/docs/switches/catalyst-6500-series-switches

Control traffic continues to be accepted as untagged on the native VLAN on a trunked port, even when the “vlan dot1q tag native” command is enabled (the native VLAN is tagged with this command) -> Answer D is correct.

Reference: http://www.cisco.com/c/m/en_us/techdoc/dc/reference/cli/nxos/commands/l2/vlan-dot1q-tag-native.html

Note: Control traffic always sent on VLAN 1 when trunking.

Question 2

Question 3

Question 4

Question 5

Explanation

If PortFast is configured on a port and it receives a BPDU the port will disable the PortFast feature (and the BPDUs are processed normally).

The “spanning-tree portfast trunk” command makes a trunk port become Forwarding immediately after coming up. Therefore this command is suitable only on trunk ports leading to Layer3 devices, e.g. routers or servers

Question 6

Comments
  1. dydx
    July 19th, 2017

    Please where are the questions?

  2. mikeSWE
    July 20th, 2017

    dydx get premium its worth it trust me

  3. CCNP boy
    July 24th, 2017

    are the Q

  4. CCNP boy
    July 24th, 2017

    Are the Qs still valid to pass this exam ? or is there a lot of new Qs ?

  5. LuciasDA
    August 14th, 2017

    STP question 2, doesn’t make sense. Most of the Exhibits are unavailable?! could you clear up the questions here please.

  6. BoZZ
    August 24th, 2017

    Q4 exibit =>

    Switch#show spanning-tree
    VLAN0001
    Spanning tree enabled protocol ieee

    STP = PVST or PVST+ = IEEE (802.1D)
    whereas RSTP = rapid pvst

  7. BoZZ
    August 24th, 2017

    Q2 Exibit:

    Switch# show spanning-tree summary

    Switch is in pvst mode
    Root bridge for:
    Extended system ID is enabled
    Portfast Default is disabled
    PortFast BPDU Guard Default is disabled
    Portfast BPDU Filter Default is disabled
    Loopguard Default is disabled
    EtherChannel misconfig guard is disabled
    UplinkFast is disabled
    BackboneFast is Enabled

    Explanation of extended system id:
    https://supportforums.cisco.com/t5/lan-switching-and-routing/why-did-we-really-need-this-quot-spanning-tree-extend-system-id/td-p/2309198

  8. WrittingSoon
    November 7th, 2017

    question 6.
    why is the priority higher. for root selection doesnt it go with the switch with the lowest priority?

  9. Mike
    November 10th, 2017

    @certprepare

    In Q1 the explanation is reversed..explanation to A) is refering to D)

  10. Marcus
    December 7th, 2017

    Another dump offer us a few more answers for Q4:
    C. The protocol is Cisco proprietary.
    D. The protocol is supported per MEC basis.
    E. The protocol does not supported by switches that utilizes EtherChannel.

    It also refers to variants A and B as correct.

    But I guess that the answer should be B and C.

    Explanation:
    – No such command “spanning-tree mode IEEE”, so A is incorrect.
    – IEEE means PVST or PVST+, both of which are Cisco proprietary. We can find the proof in “Glossary” section of CCNP book:
    PVST+ Per-VLAN Spanning Tree Plus; a Cisco proprietary version of PVST that enables PVST, PVST+, and CST to interoperate on a switch.
    So, answer C is correct.

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