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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. ramos1987
    September 18th, 2014

    PASS MY EXAM TODAY SEPT 17 with 1000/1000

    Q2, Q4, Q8 in exam today

  2. Anonymous
    September 22nd, 2014

    Great Work.. Questions are same in the exam

  3. JoseLuis
    September 23rd, 2014

    Hello. I think there is a mistake in the Q8. How will SW-C the Root whether he has a “invalid” lowest priority? When you configure a priority, for a vlan for instance, you CAN NOT introduce a priority of “1” because IOS won’t let you.

    in theory, the priorities has to be by multiples of 4096!!!!!

  4. Diego
    September 23rd, 2014

    JoseLuis it is true… it should be in this order

    0 4096 8192 …. and on!

  5. Oshikuru
    September 26th, 2014

    JoseLuis,

    This has been answered by Jason on page 1. Setting the priority for a switch in vlan 1 to 0 effectively gives a switch a priority of 1.

    This can be verified:

    Switch#sho spanning-tree vlan 1
    VLAN0001
    Spanning tree enabled protocol ieee
    Root ID Priority 1
    Address 0001.C9EB.C004
    This bridge is the root
    Hello Time 2 sec Max Age 20 sec Forward Delay 15 se

  6. Logan
    October 1st, 2014

    JoseLuis

    Yes you are right, you cant configure 1.

    but if you configure a multiples of 4096 the IOS add a value called system-id extension which is

    a number chosen according to the vlan number(this a pvst feature)

    ex: if configure “spanning-tree vlan 10 priority 4096” for vlan 10, the priority for the this switch’s vlan 10 will be show up in the output of the show spanning-tree vlan 10 command as 4106.

    based on this if you configure spanning-tree vlan 1 priority 0 command for vlan 1, the priority for the vlan 1 will be 1. I repeat this is a pvst concept so you better find out the different format between the bridge-ids of STP and PVSTP which will answer the question of why the IOS only allow multiples of 4096.

  7. jevdawg
    October 3rd, 2014

    In Q6 could C be a right answer aswell? Because when the network is running normally the cost to get to the server on VLAN 9 is 38. Now that f0/9 is down, the cost to get to vlaN 9 is now 57, wouldn’t that make frames going to vlan 9 slower?

  8. jp0427
    October 7th, 2014

    Question #5, #6 on my exam last Sunday, 2014/10/5.

    Thanks a lot 9tut. Almost all questions were from here except for two.
    Had the EIGRP and ACL 1 sims.

  9. kjkemp
    October 8th, 2014

    jevdawg,
    perhaps. slower…a little…but not SIGNIFICANTLY SLOWER…

  10. CHELAL KIPROTICH JAMES
    October 11th, 2014

    thanks to you logan,,you make me understd that concept system-id extension clearly.i av bn struggling to understd for a long time.

  11. jane
    November 3rd, 2014

    can anyone explain to me the concept of root bridge and bridge ID. This is still not clear for me….
    Thanks

  12. Cedrick MEWO
    November 4th, 2014

    Righ if you configure a priority of 0, by typing sh span it will display priority 1.

  13. kam
    November 6th, 2014

    Q-3,5,6,7 on exam today!

  14. aria
    November 10th, 2014

    6,8 and 9 today

  15. Parth Shah
    November 12th, 2014

    Q 5,7 and 10

  16. f
    November 18th, 2014

    g

  17. james
    November 19th, 2014

    can someone explain Q6… please please. thank you

  18. james
    November 19th, 2014

    whats the difference between 802.1d and 802.1q?

  19. Erika
    November 22nd, 2014

    Q1, Q2 on exam yesterday

  20. IP MAN
    November 26th, 2014

    802.1d: is a Cisco protocol for bridge and switch loops avoidence, it has same function as STP (Spanning-tree Protocol).

    802.1q: trunking protocol able to carry multiple vlan between Switches (help to carry untagged frame, frame which belong to default vlan), is a open standard and for is ISL (InterSwitch Link) use between Cisco devices. but the use is 802.1q.

  21. Cassio
    December 1st, 2014

    Please can someone explain the question 10? I didn’t understand.
    Thanks!

  22. securetelnet2223
    December 4th, 2014

    Question 10:
    Sometimes a good process of elimination help you to get the correct ans.

    A. This switch has more than one interface connected to the root network segment in VLAN 2.>>Not correct because from the given exhibit Vlan 2 has one connected interface
    B. This switch is running RSTP while the elected designated switch is running 802.1d Spanning Tree. >> Not correct because no where on the given exhibit we can tell if it is RSTP or not.
    D. This switch has a lower bridge ID for VLAN 2 than the elected designated switch. >> Not correct because no where in the given exhibit we have any info about VLAN 2 bridge ID
    The only one ans left is C and that the correct ans.

  23. Arpita
    December 5th, 2014

    can someone send me the latest dumps for CCNA to metamorphic9@gmail.com

  24. Ilya
    December 9th, 2014

    Q7 Must be: Which port state is introduced by Rapid PVST+?

    Per-VLAN Spanning Tree Plus (PVST+, or sometimes PVSTP), is a Cisco-proprietary improvement of 802.1D STP. Rapid Spanning Tree Protocol (RSTP).
    Over time, the IEEE improved STP beyond the 802.1D standard with the Rapid STP (802.1W) protocol. Then Cisco took that standard and made another proprietary improvement, creating another mode in Cisco switches: Rapid PVST+, or simply RPVST+.

    Explanation must be: “Rapid PVST+ is based on IEEE802.1D (specification as IEEE802.1D-2004) Spanning Tree Protocol (STP). But Rapid PVST+ has only 3 port states..”

    The answer will not change, but maybe there is some misunderstanding.

  25. dana
    December 12th, 2014

    Could someone please explain Q7?
    why the PVST+ has 3 states?
    and what is the discarding state?

  26. HM
    December 19th, 2014

    q2,q4,q6,q8…Dec 18

  27. faty
    December 19th, 2014

    q2 on 11 dec

  28. James
    December 19th, 2014

    Q3, 5 & 6

  29. James
    December 19th, 2014

    Today in my exam

  30. tku
    December 19th, 2014

    q4 today

  31. uday
    December 28th, 2014

    Q10 today

  32. tara
    December 30th, 2014

    hi
    which one is easier ICND1 or CCNA

  33. Greg
    January 5th, 2015

    In Q10:
    How come A is not correct?

    The port for this VLAN is in blocking state – it wouldn’t be that way if there would be only one interface connected to that VLAN, right? And it’s not root because the other one has lower interface number.

  34. MMI
    January 12th, 2015

    Pls send me the latest dumps for 200-120 CCNA Exam.
    maidulkuet@yahoo.com

  35. Lorenzo
    January 12th, 2015

    Q5, 8 Today, 1/12/14

  36. SB
    January 13th, 2015

    Can anyone explain Q6?

  37. Onarb
    January 20th, 2015

    Can anyone explain Q6?

  38. Fran
    January 25th, 2015

    Hi,

    For Q6 answer: we need to assume that the root port for vlan 3 in sw1 is f0/9. If it gets disconnected, STP will need less than 1 minute to reconverge the network and assign fa 0/7 as root port for vlan 3. Once it’s done, the traffic from host B to the server will be forwarded through the network.

  39. kapil
    January 25th, 2015

    @Tara: ICND1 is half of composite ccna exam. I am taking the test tomorrow… Please tell me would be enough to read 9tut and go for the exam?

  40. Anonymous
    January 31st, 2015

    Q8 today. Passed

  41. altaf
    February 10th, 2015

    Q8 in today exam of mine passed with 1000 marks…i think paper was so easy due to studied allot 9tut… thanks 9tut

  42. Peter
    February 13th, 2015

    Q1,5,6,7,9 yesterday. passed. tnx 9tut!

  43. Chains
    February 13th, 2015

    Hi, Peter. Where are you from ?

  44. Che
    February 15th, 2015

    Q1, Q8 on 15th Feb.

  45. Ed
    February 17th, 2015

    Is E a correct answer in Q8? Priority can only be set in increment of 4096, so how can the priority be set to 1?

  46. Anonymous
    February 20th, 2015

    @Ed
    Good question…from my study and internet research, bridge’s priority number must be in the increment of 4096. Can someone explains? Thanks.

  47. korirwn
    February 20th, 2015

    the bridge priority is between 1 and 65535 so it starts with 1

  48. MehD
    February 20th, 2015

    Can anyone tell me about Q10. why the answer 1 is incorrect?

  49. Pushpa
    February 21st, 2015

    can anybody please explain q 10 answer??

  50. Ghada
    February 24th, 2015

    Passed yesterday with score 1000 Thank God

    The exam was 51 questions, only one drag and drop about cable types, all questions are very easy just similar to 9tut.

    The lab simulations were Eigrp , ACL1 (similar to 9tut exactly) and ACL2 (modification 3 but with host B to access the finance server)

    Good luck for everyone, just be relaxed its very very easy :)

    question 8 was in it

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