CCNA – STP Questions 2
Here you will find answers to STP Questions – Part 2
Note: If you are not sure about STP, please read my STP tutorial and RSTP tutorial.
Question 1
Which term describes a spanning-tree network that has all switch ports in either the blocking or forwarding state?
A. redundant
B. spanned
C. provisioned
D. converged
Answer: D
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 2
Which two values are used by Spanning Tree Protocol to elect a root bridge? (Choose two)
A. amount of RAM
B. bridge priority
C. IOS version
D. IP address
E. MAC address
F. speed of the links
Answer: B E
Explanation
Bridge ID = Bridge Priority + MAC Address
For example:
+ The bridge priority of SwA is 32768 and its MAC address is 0000.0000.9999 -> the bridge ID of SwA is 32768:0000.0000.9999
+ The bridge priority of SwB is 32768 and its MAC address is 0000.0000.1111 -> the bridge ID of SwB is 32768:0000.0000.1111
Question 3
Which command enhances the 802.1D convergence time on ports that are connected to hosts?
A. spanning-tree backbonefast
B. spanning-tree uplinkfast
C. spanning-tree portfast
D. spanning-tree cost512
Answer: C
Explanation
By using PortFast feature, the port won’t spend 50 seconds to move from blocking (20sec), listening (15sec), learning (15sec) and finally forwarding but will jump directly to the forwarding state. This feature should be used on ports connected to hosts only because hosts surely don’t send BPDU. An example of configuring PortFast on an interface is shown below:
Sw(config)#interface FastEthernet0/1
Sw(config-if)#spanning-tree portfast
Question 4
Which two of these are used by bridges and switches to prevent loops in a layer 2 network? (Choose two)
A. 802.1D
B. VTP
C. 802.1Q
D. STP
E. SAP
Answer: A D
Explanation
Both 802.1D and STP are referred to the STP standard which is used by bridges and switches to prevent loops in a layer 2 network.
Question 5
Refer to the exhibit. The output that is shown is generated at a switch. Which three of these statements are true? (Choose three)
A. All ports will be in a state of discarding, learning or forwarding.
B. Thirty VLANs have been configured on this switch.
C. The bridge priority is lower than the default value for spanning tree.
D. All interfaces that are shown are on shared media.
E. All designated ports are in a forwarding state.
F. The switch must be the root bridge for all VLANs on this switch.
Answer: A C E
Explanation
From the output, we see that all ports are in Designated role (forwarding state) -> A and E are correct.
The command “show spanning-tree vlan 30″ only shows us information about VLAN 30. We don’t know how many VLAN exists in this switch -> B is not correct.
The bridge priority of this switch is 24606 which is lower than the default value bridge priority 32768 -> C is correct.
All three interfaces on this switch have the connection type “p2p”, which means Point-to-point environment – not a shared media -> D is not correct.
The only thing we can specify is this switch is the root bridge for VLAN 3o but we can not guarantee it is also the root bridge for other VLANs -> F is not correct.
Question 6
What is one benefit of PVST+?
A. PVST+ reduces the CPU cycles for all the switches in the network.
B. PVST+ automatically selects the root bridge location, to provide optimization.
C. PVST+ allows the root switch location to be optimized per vlan.
D. PVST+ supports Layer 3 load balancing without loops.
Answer: C
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 7
Which IEEE standard protocol is initiated as a result of successful DTP completion in a switch over FastEthernet?
A. 802.3ad
B. 802.1w
C. 802.1Q
D. 802.1d
Answer: C
Explanation
Dynamic Trunking Protocol (DTP) is a Cisco proprietary protocol for negotiating trunking on a link between two devices and for negotiating the type of trunking encapsulation (802.1Q) to be used.
Question 8
What value is primarily used to determine which port becomes the root port on each non-root switch in a spanning-tree topology?
A. lowest port MAC address
B. port priority number and MAC address.
C. VTP revision number
D. highest port priority number.
E. path cost
Answer: E
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 9
When PVST+ in work on VLAN1 of the switch, what will affect on selection of one of switches in the VLAN as root-bridge?
A. Lowest IP address
B. Highest MAC address
C. Lowest MAC address
D. Highest IP address
Answer: C
Explanation
The two values used to select the root bridge are Bridge Priority & MAC address (the lower is better) -> C is correct.
Question 10
Refer to the exhibit. A network administrator wants Switch3 to be the root bridge. What could be done to ensure Switch3 will be the root?
A. Configure the IP address on Switch3 to be higher than the IP addresses of Switch1 and Switch2.
B. Configure the priority value on Switch3 to be higher than the priority values of Switch 1 and Switch2.
C. Configure the BID on Switch3 to be lower than the BIDs of Switch1 and Switch2.
D. Configure the MAC address on Switch3 to be higher than the Switch1 and Switch2 MAC addresses.
E. Configure a loopback interface on Switch3 with an IP address lower than any IP address on Switch1 and Switch2.
Answer: C
Explanation
To become root bridge, a switch must have lower Bridge ID (BID) than that of the others. The Bridge ID = Bridge Priority + MAC address; but MAC address is a fixed value so we can only change the BID by changing the Bridge Priority of that switch.
Question 11
Which port state is introduced by Rapid-PVST?
A. learning
B. listening
C. discarding
D. forwarding
Answer: C
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 12
At which layer of the OSI model is RSTP used to prevent loops?
A. data link
B. network
C. physical
D. transport
Answer: A
Explanation
RSTP and STP operate on switches and are based on the exchange of Bridge Protocol Data Units (BPDUs) between switches. One of the most important fields in BPDUs is the Bridge Priority in which the MAC address is used to elect the Root Bridge -> RSTP operates at Layer 2 – Data Link layer -> A is correct.
Question 13
Refer to the exhibit. At the end of an RSTP election process, which access layer switch port will assume the discarding role?
A. Switch3, port fa0/1
B. Switch3, port fa0/12
C. Switch4, port fa0/11
D. Switch4, port fa0/2
E. Switch3, port Gi0/1
Answer: C
Explanation
In this question, we only care about the Access Layer switches (Switch3 & 4). Switch 3 has a lower bridge ID than Switch 4 (because the MAC of Switch3 is smaller than that of Switch4) so both ports of Switch3 will be in forwarding state. The alternative port will surely belong to Switch4.
Switch4 will need to block one of its ports to avoid a bridging loop between the two switches. But how does Switch4 select its blocked port? Well, the answer is based on the BPDUs it receives from Switch3. A BPDU is superior than another if it has:
1. A lower Root Bridge ID
2. A lower path cost to the Root
3. A lower Sending Bridge ID
4. A lower Sending Port ID
These four parameters are examined in order. In this specific case, all the BPDUs sent by Switch3 have the same Root Bridge ID, the same path cost to the Root and the same Sending Bridge ID. The only parameter left to select the best one is the Sending Port ID (Port ID = port priority + port index). In this case the port priorities are equal because they use the default value, so Switch4 will compare port index values, which are unique to each port on the switch, and because Fa0/12 is inferior to Fa0/1, Switch4 will select the port connected with Fa0/1 (of Switch3) as its root port and block the other port -> Port fa0/11 of Switch4 will be blocked (discarding role).
If you are still not sure about this question, please read my RSTP tutorial.
@SARA
default value of bridge priority is always 32768…memorise it
I PASSED CCNA EXAM TODAY THANKS TO ALL MIGHTY ALLAH
960/1000
Q7 in the exam
Hi guys and 9tut. I have a question I saw in Jericho and bruce dump but has two different answers in both dumps.I am confused as to which is the right answer, please help. Question is below:
In which circumstance are multiple copies of the same unicast frame likely to be transmitted in a switched LAN?
a) When a dual ring topology is in use
b) In an improperly implemented redundant topology
c) After broken links are established
d) When upper-layer protocols require high reliability
e) During high traffic periods.
In Bruce dump 564q it says the answer is a) but in Jericho 632q dump it says b). Whats the correct answer?
Thanks to OCSIC and XALLAX, I noticed u had discussed this in one of the comments and that the correct answer should be ” in an improperly reduntant network topology”. Keep up the comments guys, very helpful. Plaaning to write my exams june 20th and plan to make a donation to 9tut for the help.
I passed my ccna exam today Praise be to God! Thank you Jesus! and thanks to 9TUT for the tutorials and explanations, great site and thanks to xallax for your explanations to questions and thanks to http://www.examcollection.com for the dumps. Pls guys lets donate and help to keep this site up!
48 ques for exams including 3 simulation, I had EIGRP, Acesslist2 and VTP. Make sure the practice the simulation, use packet tracer or gns3. Best wishes to all!
I am taking my test in a few days, can anyone send me the latest dumps at hammadrn@hotmail.com.
@9tut
I am unsure about Q6:
C. PVST+ allows the root switch location to be optimized per vlan.
D. PVST+ supports Layer 3 load balancing without loops
C was correct but why not D? PVST+ can can create instances influenced by Vlan and therefore send L3 packets over more than 1 route (hence load balancing). It is by nature loop free….
Question 5 is wrong.
By the looks of the output it’s A,C,E,F as it clearly states “this is the root bridge” and all ports are in the forwarding state. Correct me if i’m wrong?
This needs correcting :-)
hmmm however after further thought it may not be the root bridge for ALL VLANS as you can configure specific bridges to be the root vor different VLANS right?
With the use of pvst+ :-)
I need to go to sleep…………studying too much!
question 5 lol¡
Q5 Answer F is indeed wrong, as it said the switch must be the root bridge for ALL VLANs. While it’s true that it’s the root bridge for VLAN30, i.e. “This bridge is the root,” it may not apply to the rest of the VLANs. I recently completed a lab exercise, and it turns out a switch is root bridge for a VLAN, but not a root bridge for another VLAN.
^
As different ports assigned to different VLANs. Different ports lead to different calculations which give different outcome of whether root bridge or not.
hello everybody, can smbody explain which cisco propietary stp protocol is (are) compatible with ieee standart stp protocol i know stp and rstp are compatible bat pvst+ ,pvst, with stp and rstp ????? pls
thanks
Please clarify Q10 of STP Questions 2.
Q10 refers to Rapid-PVST, which does not appear to exist according to Todd Lammles guides or the Cisco site. There is however a Rapid-PVST+ which is a Cisco implementation of RSTP.
Rapid-PVST+ only has four states –
Blocking, Learning, Forwarding and Disabled.
It does not have the Listening state, and Discarding does not appear to be a relevant.
So From the answers given, Listening and Discarding do not relate to the protocol. There is no correct answer. Your answer of Discarding is incorrect, as it is not a Rapid-PVST state.
Your explanation refers to PVST+ which is a Cisco legacy implementation using the port states; Disabled, Blocking, Listening, Learning and Forwarding. It is different to Rapid-PVST, and cannot be answered from the choices you have offered of: Learning, Listening, Discarding and Forwarding
Cisco Nexus 5000 Series Switch CLI Software Configuration Guide page 8-11 states:
“Each LAN port on a software using Rapid PVST+ or MST exists in one of the following four states:
• Blocking—The LAN port does not participate in frame forwarding.
• Learning—The LAN port prepares to participate in frame forwarding.
• Forwarding—The LAN port forwards frames.
• Disabled—The LAN port does not participate in STP and is not forwarding frames.”
Please could you clarify which version of STP the question should relate to, as it has led to several hours of research across Cisco and different books to identify the confusion inherent in the question.
There is of corse the possiblity the question should read:
Which port state is REMOVED by Rapid-PVST+?
From the answers given, Listening would then be correct.
Apart from that – Great site with a lot of effort. Thanks
Frank T
Me again – Sorry after all that writing, I referred to Q10, when it should be Q11.
Q11. Which port state is introduced by Rapid-PVST?
Frank T
DID IT!!…907…thx 9tut!!!!..CCNA certified….tons of questions from this site…read from top to bottom every question, because you will not know what pops up…q3, 4 and 8 on exam…study concept…good luck to all…can’t stress enough…read EVERY question on this site…
i need to ask one qus…
http://i.imgur.com/ux76V.png
in shekhar dumps ans. is C but ..in other dumps i see answer is B …so can anyone tell me whta is the exact ans. n y ???
thnx in advance :) :)
@kushal arora:
i believe, the question in your images differs from the question, where B is the right answer ;-)
take a look:
http://tinypic.com/r/2ros313/6
in my image, B is the correct answer, because they ask for SOME redundany to increase reliabiliy. in your image they ask for MAXIMUM RELIABILITY.
hope, i’m right and helped you.
Which two data link protocols are supported by cisco ios software for IPv6?
A.Frame Relay
B.PPPv6
C.HLDCP
D.ATM
E.FDDI
F.MPLS/6PE
Answer:A and C
Can any one please explain why A and E are answers. I find below article but I dont know is reliable or not. (http://ipv6int.net/systems/cisco_ios_router-ipv6.html)
Cisco IOS supports a variety of IPv6 over data link layers, including:
Ethernet (Ethernet, Fast Ethernet, Gigabit Ethernet, and 10-Gigabit Ethernet)
Frame Relay
PPPv6
HLDCP
ATM
FDDI
MPLS/6PE
@9tut,xallax,anyone
in q1 why can’t the ans be D E F
in q13 what are “port index” and “Port values” can we configure them manually if yes, how?
plz help me I hv my xm in few days………tnx in advance
ohh sry in q5 why can’t the ans be D E F
in q5 how can a port be in three different states : discarding, learning and forwarding…???
@anyone
in q13 in explanation it is said that “fa0/12 is inferior to fa0/1″ can anyone plz tell me how..???
@ankushk
Q5 it can be in one of those 3: discarding, learning OR forwarding
Q13 the interface ID is the number the interface has (0/1, 0/12, 2/2, etc). the lower the ID, the better it is (0/1 < 0/24 < 2/2)
@9tut,xallax,anyone
could you please explain this question:
Which two data link protocols are supported by cisco ios software for IPv6?
A.Frame Relay
B.PPPv6
C.HLDCP
D.ATM
E.FDDI
F.MPLS/6PE
Answer: A and C
Just cleared my exam with a perfect perfomance (1000/1000)…..GRATITUDES: First and foremost to the almighty God for everythng he has been since i started preparing for this exam abt a year ago! the Todd lamlle (6th edition), this book gave me the foundation i needed and i consider myself one of the fastest subnetting geek thanks to Todd’s chapter on subnetting…then seriously, who wud forget this guy (9tut) thanks alot man,i finished my exam 40 minutes before time thanks to the speed you gave me in simulations…examcollection, thanks alot guys i ddint see any qn that i hadnt met in the dumps before, then the CBT nuggets videos….they cleared (enhanced) all of the concepts i have learned from all of the materials i have already mentioned! thank you all so much…..i will DONATE when i get my credit card! keep the good work going 9tut
ABOUT MY EXAM:
I had total of 50 questions….
Had three simulations….ACL2, same as here at 9tut but modified as the third table of modifications above and i was dealing with host B plus different IP addresses, EIGRP almost the same as here, had to change the AS in router Home 2 from somethng 21 to 221 and add the appropriate networks also i had to delete and add some networks from router Home 1 (central router) and finaly the VTP…same as here just different question to follow the same procedures in resolving
NB: i ddnt see anythng that i had not come across before
for any other enquiries find me at ropamson@gmail.com …..best of luck for everybody working on CCNA
Q13 was in my ICND 2. I fail but was very near close guys 804, was my first attempt though (Im going in again). See there are lot of question came from 9tut CCNA questions rather than 9tut ICND 2. So whoever preparing for ICND 2 make sure you master all the CCNA questions here, then add those from icnd 2 then u r ready to clear it (don’t forget you Prep cisco press book points). Just my two cent.
I have the same issue with Q5…dumps differ on answers, however I think that F can also be right….I am writing on 23 October, hope I dont get this question….
After reading the Q5 thorougly, F cant be right, because what on earth does the following mean: This switch must be the root bridge for all vlans on this switch….maybe if it was:
The switch must be the root bridge for all vlans in the Local network…else f is implying that PER VLAN stp is being used.
Passed CCNA today 933/1000, Q13 is my 1st question in the exam
9tut rocks!~
ACL SIM, VTP and EIGRP SIM. I finished the exam 15 min before specified time!
Q7.
C is correct, but a side note; There could be a successful DTP completion *WITHOUT* 801.1Q (trunking) is used.
dynamic auto – the port will negotiate the mode automatically, however, it prefers to be an access port
dynamic desirable – the port will negotiate the mode automatically, however, it prefers to be a trunk port
Hence:
dynamic auto + dynamic auto = access
dynamic auto + dynamic desirable = trunk
dynamic desirable + dynamic desirable = trunk
dynamic auto or dynamic desirable + trunk = trunk
dynamic auto or dynamic desirable + access = access
https://supportforums.cisco.com/thread/2000727
Q7 continued;
Cause you can connect two switches using access-ports if you’re only using the native vlan.
Q5: Is “A”, a right answer?
Q5: A – states “All ports will be in a state of discarding, learning or forwarding.”
However, the output indicates that the protocol is “rstp.” Correct me if I am wrong, but doesn’t rstp define additional port roles of “alternate and backup?”
So shouldn’t A- read: All ports will be in a state of discarding, learning, forwarding, alternate, and backup?
@xallax
can you pls explain q13 why switch 3 GI0/2 cannot be in discarding role.
Pls help thanks.
@13
gi0/2 is in discarding mode BUT that’s not one of the given options to pick from
hi i am writing ccna exam before 2012. if anyone interested pls send or contact me at banglaland@gmail.com for reinstatement. i will appreciate any offer thanks
@mce
You are mixing port roles & port states, so port state will be only discarding, learning or forwarding (discarding merges blocking, listening & disabled from STP).
Port roles are root, designated, alternate or backup (alt. and backup replaced blocking)
could you please explain this question:
Which two data link protocols are supported by cisco ios software for IPv6?
A.Frame Relay
B.PPPv6
C.HLDCP
D.ATM
E.FDDI
F.MPLS/6PE
Answer: A and C
pls..explain
email :tamilarasiek@gmail.com
Q5- The switch is running RSTP not Rapid-PVST so the same switch will be the root bridge for all the vlans.
Also since the given switch is the root bridge all its ports will be designated which in turn will only be in forwarding state. So option A is wrong. Option F is correct.
@9tut
Q5. the answer A is wrong..modify as soon
Q5 up !
@9tut :
I do agree with my fellows about question 5.
“F. The switch must be the root bridge for all VLANs on this switch” should be a correct answer since we are on RSTP and not on PVST.
What do you think ?
TY 9tut.
Today I have passed the CCNA. (860/825)
50 questions 3 labs (VTP, EIGRP, ACL). 35 from 9tut.
Also thanks a lot Brar and Sekhar (still valid from examcollection)
Ty again 9tut
from here Q 4, 8
Q5 – I agree with above comments, answers should be C E F
With reference to Q5, it’s rapid pvst so option F is false!
thanks you make question easy for teachers and students thanks