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CCNA – STP

May 5th, 2015 Go to comments

Note: If you are not sure about Spanning Tree Protocol, please read our Spanning Tree Protocol STP Tutorial (Premium Tutorial).

Question 1

Explanation

First by comparing their MAC addresses we learn that switch B will be root bridge as it has lowest MAC. Therefore all of its ports are designated ports -> C & D are correct.

On the link between switch A & switch C there must have one designated port and one non-designated (blocked) port. We can figure out which port is designated port by comparing their MAC address again. A has lower MAC so Fa0/1 of switch A will be designated port while Fa0/1 of switch C will be blocked -> B is correct.

Question 2

Explanation

The path cost to the root bridge is the most important value to determine which port will become the root port on each non-root switch. In particular, the port with lowest cost to the root bridge will become root port (on non-root switch).

Question 3

Explanation

Per VLAN Spanning Tree (PVST) maintains a spanning tree instance for each VLAN configured in the network. It means a switch can be the root bridge of a VLAN while another switch can be the root bridge of other VLANs in a common topology. For example, Switch 1 can be the root bridge for Voice data while Switch 2 can be the root bridge for Video data. If designed correctly, it can optimize the network traffic.

Question 4

Question 5

Explanation

If we connect two switches via 2 or more links and do not enable STP on these switches then a loop (which creates multiple copies of the same unicast frame) will occur. It is an example of an improperly implemented redundant topology.

Question 6

Explanation

Answer A is not correct because Host A & B can access the server in VLAN 9 via Switch1 -> Switch2 -> Switch3 path.

Answer B is not correct because VLAN3 can communicate with other VLANs via port Fa0/7 on Switch1

Answer C is not correct because Host B can transfer files to VLAN 9 via Switch1 -> Switch2 -> Switch3 path. All the links on this path are FastEthernet so we cannot it would be significantly slower.

Answer D is the best choice as Fa0/9 on Switch1 may be the main path to reach VLAN 9 and it is in forwarding state. If the cable connected to Fa0/9 is disconnected, STP needs less than a minute to re-converge (moving from blocking -> listening -> learning -> forwarding state). Then the network function would resume and Host B will access VLAN 9 via Switch1 -> Switch2 -> Switch3 path.

Question 7

Explanation

PVST+ is based on IEEE802.1D Spanning Tree Protocol (STP). But PVST+ has only 3 port states (discarding, learning and forwarding) while STP has 5 port states (blocking, listening, learning, forwarding and disabled). So discarding is a new port state in PVST+.

Question 8

Question 9

Explanation

Spanning Tree Protocol convergence (Layer 2 convergence) happens when bridges and switches have transitioned to either the forwarding or blocking state. When layer 2 is converged, root bridge is elected and all port roles (Root, Designated and Non-Designated) in all switches are selected.

Question 10

Comments (50) Comments
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  1. chris
    March 1st, 2015

    in reponse to q10, I think the reason it is not answer a is because even if there was another interface within the vlan, it doesn’t explain why port fa0/10 is in alternate disabled mode. fa0/10 is disabled because it has a higher cost to the root bridge within that vlan.

  2. Anonymous
    March 7th, 2015

    Question 8 is BS you CANNOT set the priority to one the lowest is 0 and then 4096

    AHCORESW(config)#spanning-tree vlan 10 pri
    AHCORESW(config)#spanning-tree vlan 10 priority 1
    % Bridge Priority must be in increments of 4096.
    % Allowed values are:
    0 4096 8192 12288 16384 20480 24576 28672
    32768 36864 40960 45056 49152 53248 57344 61440
    AHCORESW(config)#

  3. Buchi
    March 8th, 2015

    Q8: Yes, however:
    Bridge ID priority note as per cisco, 32769 (default bridge priority plus system ID extension of default VLAN1).

    0 + 1 (vlan 1 by default) = priority of 1

    Note priority is already “set” in CLI and accepted as such…….

  4. Buffon
    March 18th, 2015

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  5. Apush
    March 18th, 2015

    Passed my CCNA exam today (18th Mar)… Q2, Q4 and Q8 in exam

  6. Sunil
    March 19th, 2015

    I have new vce dumps but dont have vce player latest version

  7. john doe
    March 25th, 2015

    Question 10 is Arguable…..

  8. Arya
    March 28th, 2015

    ^ You know nothing John Doe

  9. dude
    April 8th, 2015

    passed with 988/1000. read todd lammle book do lab practices and revise 9tut questions. you will pass most of the questions are from this site

  10. ian- zambia
    April 8th, 2015

    hi guys, am currently studying for my CCNA and your comments have highly motivated me.

  11. Siaulius
    April 12th, 2015

    Sunil, could you share vce dumps, thanks in advance siaulietisss@yahoo.com

  12. Amit Upadhyay
    April 15th, 2015

    Please explain question no 6

  13. SaedAdi
    April 17th, 2015

    Q4,6,8,9

  14. Tomáš
    April 20th, 2015

    to Amit Upadhyay:

    When the link fails, STP will be recalculated in order to find alternate and loopfree path. This time is usually les than 1 min. With rapid STP the time is even lower.

  15. Nadith
    April 26th, 2015

    Q1 when we selecting Designate port,what is the correct logic?
    I know all the ports in root bridge (excluding RP)are designated ports.
    But we select a DP on a network segment (link) what is the sequence we need to consider?
    as a example lets say terms of cost is equal to both A and C ports then what we need to check next..
    1st.terms of cost
    2nd. interface ID(number)
    3rd. bridge id
    4th. MAC address

    is this sequence is correct???

  16. Beel
    April 27th, 2015

    Hi Nadith,

    the correct sequence is :

    1- Cost to root bridge.

    2- Lost Bridge ID ( Bridge priority + MAC address)

    3- Lowest Interface number.

  17. Nadith
    April 28th, 2015

    Thank you ,Beel!!

  18. Laura
    April 28th, 2015

    -to select a designated port , at first we must find the lowest bridge ID ( priority and then MAC @), not the cost to root bridge.

    -to select a root port we need to choose the lowest cost to root bridge, but if it’s the same, we check the bridge ID (that’s why it saids the links are operating at the same bandwidth).

  19. Rakan
    May 9th, 2015

    Thanks god I passed my exam today with 980/1000 the exam was very easy, but you should focus on the questions.

    My advice to pass the exams is to answer the question fast, but make sure you choose the right answer before you move to the next one; also, the important thing to pass the exam is don’t be nervous relax my friend, and think about the succeeding only and you are good to go.

    peace ^_^

  20. someguy
    May 12th, 2015

    Q6. I see a device in Vlan3 trying to communicate with a device in Vlan9…wouldn’t this traffic have to pass through a router, thus making Fa0/9 irrelevant in this scenario?

    Maybe I’m missing something here, please enlighten me.

  21. Hicham
    May 19th, 2015

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  22. TMayedzenga
    May 27th, 2015

    Passed with 972/1000 thanx to 9tut and Watson

  23. Hiwot
    May 27th, 2015

    TMayedzenga,

    Would you post the questions you remember please? Thanks

  24. FayazH
    June 5th, 2015

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  25. sharm
    June 10th, 2015

    hi. can you email me the latest dumps? thank you so much! :)

  26. masud
    June 20th, 2015

    anyone has better answer for q.10 thank you.

  27. Me
    June 23rd, 2015

    Q3,4 & 8 on exam today. Got 1000 so answers are good. (labs: ACL and EIGRP – 2 friends before me stated NAT as well.)

    Would also like to note a question I did not see on 9tut. Fairly basic, but worth note. Not verbatim or course, but: How is a private address handled if it is placed on an ISP WAN interface. A: (although strictly not true) Private addresses can not be routed on the public internet backbone (or something to that effect).

  28. Questions Today
    June 24th, 2015

    Q3,Q7 and Q8 was in exam. Praise The Lord and thnx 9tut passed on 24th june 986/1000.
    Some new questions to be observed:
    What will happen if a private IP address is assigned to a public interface connected to an ISP?
    A. Addresses in a private range will be not be routed on the Internet backbone.
    B. Only the ISP router will have the capability to access the public network.
    C. The NAT process will be used to translate this address to a valid IP address.
    D. A conflict of IP addresses happens, because other public routers can use the same range.
    Answer: A
    What are three values that must be the same within a sequence of packets for Netflow to consider
    them a network flow? (Choose three.)
    A. source IP address
    B. source MAC address
    C. egress interface
    D. ingress interface
    E. destination IP address
    F. IP next-hop
    Answer: A,D,E

  29. winnie
    June 25th, 2015

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    July 1st, 2015

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  31. OW
    July 2nd, 2015

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  32. Anonymous
    July 3rd, 2015

    why we are speaking lie ourself wih 9tut?:-)

  33. Anonymous
    July 4th, 2015

    what kind of lies my friend

  34. Mohammed
    July 4th, 2015

    I see that this is a good website for preparing for the CCNA industry exam

  35. BoltThrower
    July 5th, 2015

    Question 6 must be wrong! If the cable is disconnected from Host B to its switch…absolute no network communication can occure. So answer A must be correct rather than answer D which is listet here.

    Answer D would be only correct if the cable is re-plugged, but the question does not assume that

  36. Anonymous
    July 5th, 2015

    BoltThrower, STP will reconverge to use Fa0/7 as F0/9 failed. STP reconverges in about 50 seconds, therefore D is correct.

  37. Bariq
    July 6th, 2015

    The answer of the question 6 is right because there redundant link ( backup) in switch 1 and it will be work after about 50 second

  38. Bariq
    July 6th, 2015

    The answer of question 8 is wrong because the allowed values of priority are (4096 , 8192 12288 , 16384 , 20480, 24576, 28672 , 32768 , 36864 , 40960 , 45056 , 49152 , 53248 , 57344 , 61440)

  39. BoltThrower
    July 6th, 2015

    Yep, you are right guys…I thought fa0/9 would be the link between Host B and the switch (therefore no LAN connection)…but that is not the case….

  40. @BoltThrower
    July 11th, 2015

    The topic is STP, of redundant link.
    if one link is down still communication can be done. by other connecting links.

  41. TNA
    July 12th, 2015

    can anyone explain the Q 10

  42. 9tut
    July 12th, 2015

    @all: We had to move all the questions and answers out of 9tut. We can only keep the explanation. You can download the questions and answers at: https://mega.co.nz/#!wt9kVCjL!vvp79FTtjsqfpCgq0uTOTKlE6_qsLY6C_m163sNGs_s

  43. abc
    July 14th, 2015

    why question are not displayed???????????????

  44. rodrigosub
    July 15th, 2015

    Hi

  45. Morgan
    July 15th, 2015

    Can someone tell me why I cannot see the question anymore??

  46. Peace & Love
    July 17th, 2015
  47. Morgan
    July 21st, 2015

    Thanks Peace & Love, I appreciate :-)

  48. pop
    July 21st, 2015

    I can’t see the questions ?

  49. Alisher
    August 4th, 2015

    Can someone explain me quiestion 1 please? I didn’t get it. Why is switch a has a lower mac when it seems to me that mac address of switch c is lower?

  50. Alisher
    August 4th, 2015

    I got it. I was a bit careless.

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