OSPF Questions 5

Q7: I don’t think answer D is correct. Output from RTA shows that RTC is in 2-WAY/DROTHER state which means RTA must communicate with RTC via DR/BDR. Should the RTA be BDR, it would show FULL/DROTHER state on the RTA output.
None of the answers seems to me correct.

I agree with Tomas. I would say that RTA is another DROTHER router.

Its one of those “most correct answers”. RTA being the BDR is the only option that fits, so it must be the answer. You may not know that it is from the out put, but you also do not know that it is DROTHER either.

Hello Friends,

I just started to study the ROUTE test after taking almost two years off from passing the CCNA. I am planning to take the ROUTE test in two months. Are the Sims, Drag and Drop, Questions, and everything else on this site still valid for the ROUTE test?

Thank you all!

Question number 9 in incorrect. answer is “C. Dev-3 is the DR because it has a higher OSPF router priority.”. Reason is that the priority that is highest wins. Dev-3 is the one with priority number 2, and dev-1 is priority number 1. The router with the highest priority wins, this is even reflected in the output, as dev-3 is the winner and is currently in the FULL/DR state. Dev-3 would have won anyways, because it had the highest RID in the 172 address range, vs dev-1 10. address.

Reference cisco press 642-902, page 276, the below paragraph –

The OSPF priority defines the priority when choosing a DR and BDR. Configured with
the ip ospf priority value interface subcommand, the higher number (ranges from 0–255)
wins. Also, a priority of 0 has special meaning: it prevents that router from becoming the
DR or BDR. By configuring OSPF priority of 0 on routers that do not have a PVC connected
to each other router (such as R2, R3, and R4 in this case), the other routers (R1 in
this case) will be the only routers eligible to become the DR.

Also, in this explanation of question 9 -

Notice that the Priorities shown in the output above are the priorities of the neighbors so router the priority of router Dev-1 is 2 while the priority of Dev-3 is 1 -> the priority of Dev-1 is higher than that of Dev-3 -> Dev-1 is the DR.

is wrong, as dev-1 has a priority of 1 in the ecample, and dev-3 has a priority of 2 in the example. Revise the explanation and answer, or revise screen shot to support the explanation.

@blah blah:

You should check again with your explain. I strongly agree with 9tut’s answer.

Output from Dev3 shows detail about its NEIGHBOR. In this case, Dev-1 has priority 2 and the state colum tell that Dev-3 is connected to the DR.

@Blah Blah

Question 9 answer is correct. When you run the command ‘show ip ospf neighbor’ you have to remember it shows the priority of existing neighbors not the priority of the router you are running the command on.

Q 10 eixbhit updated with the correct one..Thanks for pointing it, In return i will happily explain Q24 to you, please bear with me: On a broadcast or multi access network the router with the highest OSPF priority on a given segment will become the DR for that segment. However if all routers have the same default priority (as in the example of Q 24) the router with highest Router ID (RID) will be the Designated router DR.The Router ID is determined by the highest IP address on any interface of the router at the moment of OSPF election.Since the concept is clear enough I’ll leave you to do the math.

Q7
I think that D is wrong answer. BDR and DROTHER form FULL adjacency not 2-WAY. Only DROTHER routers form 2-WAY adjacency to each other. So I think there is one DR, two DROTHER routers and none BDR on this segment. RTA is not BDR.
C is correct answers.

Please comment or correct the answer.

@Me
D is the correct answer. Look at the output and where it was run from. The command was run on RTA.
Remember on ALL multi-access networks a DR *and* a BDR are elected. If you are on a router and issue the ‘show ip ospf neighbor’ command and you see that all other routers are either a DR or a DROTHER, guess what…………..you are the BDR.
Its a process of elimination question.

@Me (again)
I see what you are saying, but this is Cisco and this is the type of question that they love asking.

Q7
RTC has a priority 0, so it doesn’t participate in DR/BDR election process. RTA must be BDR. ( btw, why is there two output interfaces ? Eth0, Eth1 )

I am giving ccnp route is the wheel man dump still valid.What are other valid dumps along with digitaltut.Are all answers correct on wheelman dump?And does any one have packet tracer/GNS3 examples for the lab practice

RTA will not establish an OSPF adjacency with RTB. (Right answer as per this website).

RTA will not accept OSPF hello packets from RTB. ( This should be the right answer to me, beacuse on a passive interface RTA will not accept hello packet. and as a result no adjacency will be established. As this come first in the procedure this should be selected as right answer.

Wait for your comments
. Thanks

“RTA will not accept OSPF hello packets from RTB” means that RTA is refusing the hello packets. If that is the case, you can see that on a debug. RTA will simply not participate in the ospf process on the passive interface thus will not be in a position to accept or deny hellos. Answer A is correct as stated.

@ Me
t think that there is something wrong with the question. true only two DROTHERS form 2way state relationship if RTA is the BDR then what is reflected there should be FULL/DROTHERs… so what happened to BDR?

For Question 6; I believe answer D is correct:

D. RTA will send OSPF updates, but will not establish an adjacency with RTB.

Why? Because you are enabling OSPF with the mask that covers both interfaces and you are defining only F0/0 as passive; so RTA could, eventually send OSPF updates to router C out the interface F0/1.

@GreenScorpionCR
You are 100% right. Because you think about whole topology – in this case router RTA send updates to RTC and not establish an adj with RTB.
BUT – This is CISCO – and they make many foolish questions. When they create this question – they think only about router RTB and RTA.

@GreenScorpionCR, you are correct. But I suspect the question itself is inaccurate, maybe it was only talking about the F0/0 interface. If so, then the correct answer is A.

@johnmaxwell, for question 7: if RTA is configured with priority 0, then there will not be any BDR. So RTA and RTC will not participate in the election because their priorities will be 0. RTB is the only one that has non-zero priority, making it the BDR. From the output, RTA and RTC are in a 2WAY/DROTHER state, which means that RTA is not the BDR (i.e., its priority is set to 0), so the answer on this site is wrong. The only way that RTA is the BDR is if we take into consideration that the neighbor relationship with RTC has only been up for 12 seconds, so they still did not move past the 2WAY state (for example, if you were to run the sh ip ospf ne command again after a while, you would find it FULL/DROTHER). Although I think it’s highly unlikely that a 2WAY state is stuck at 12 seconds =/.

In your Q9 output change dev-3 to dev-1 and dev-1 to dev-3. You have swapped them and they confusing everyone

Q7:
Answer D is wrong. Assuming:
1. 2-WAY/DROHTER relationships with RTC
2. ROUTE Quick Reference says “Each router in the routing domain shares its LSAs with all other routers”

I can conclude, that Answer C “Router RTA and neighbor 192.168.45.2 are exchanging OSPF LSAs” IS CORRECT. Any comments?

Hi
For question 7 is really simple . First check the priority if its zero 0 as in case of router RTC it will not take part in the DR/BDR election so RTC is excluded.
Now we are sitting on RTA and typing the neighbor command that tells us RTB is FULL/DR so it can be concluded that RTA will be a BDR which is option D and option D tells us about that unless otherwise stated.
Comment please!

Question 7 is intrested to know the state of the router as if you scroll down to question 8 , they omit the state output

@Imran shahid
There doesn’t have to be a BDR. You can have it so that there’s only a DR and no BDR. The thing that makes RTA not a BDR is because it was a 2WAY relationship with RTC. DRs and BDRs form FULL adjacencies with all neighbors. Since it RTA shows a 2WAY relationship with RTC, then RTA must be another DROTHER.

Answer C is wrong as well because DROTHER’s do not exchange OSPF LSAs with each other.

Q9 is wrong.

The correct answer and explaniation:

OPTION C is the correct:

The priority of router Dev-1 is 1 while the priority of Dev-3 is 2 -> the priority of Dev-3 is higher than that of Dev-1 -> Dev-3 is the DR.

Question 8
Why FULL/BDR and not 2-WAY/BDR?

Because RTB will form an adjacency with BDR. Topology information is exchanged directly with DR and BDR and hence the state FULL.

Q2

Answer B is also correct as the network advertised by 10.0.0.0 is /8 and not /24 … can somebody guide me . thanks

@ kashif. sometimes these answers might seem similar or even confusing, but it is always advisable to choose the best that apply and that is Answer A.
Even if the wildcat masks are correct, the implementation of that network topology can never function correctly if the subnets are configured in the wrong areas. Thus none of them will be able to form neighborship and/or adjacency with one another. Think of it as a road map to a certain city and routers A and B has been mislead (ie , misconfigured ), they will never get to router C which is the backbone area and their common neighbor.

Q7, process of elimination:
A. Router RTA is directly connected to interface 192.168.45.1.
No it is not that is the ID of router B. incorrect
B. Neighbor 192.168.45.1 has changed its OSPF priority number.
No it has not it is the default. incorrect
C. Router RTA and neighbor 192.168.45.2 are exchanging OSPF LSAs.
Not according to the output that would be full/drother. incorrect
D. Router RTA is the BDR.
this is all that is left that is not definitely wrong. Suggests RTA has a default priority but came online after RTB was elected DR and is not yet fully adjacent with RTC. DR/BDR elections do not preempt therefore with default priority RTA will become BDR and eventually form an adjacency with other ospf speakers on the segment. if RTA had a zero priority it would not become BDR but that is not a given option.

Q7:

I’d say what they try to represent is a shared medium, like Ethernet. And there you always have a DR/BDR selection. Since there’s already a DR, and a DROTHER/2WAY…. it’s so easy to see that RTA is a BDR.

Why some say C is the answer is a complete mystery to. Exchanging LSAs on a shared medium is with the DR, and RTA is not the DR.

Answer D is the only right question.

About the comment of Imran shahid. That is true.

Then a comment “There doesn’t have to be a BDR.”, also true, BUT we don’t know the priority on RTA right?

One of them is set to 0, the default is 1, so since they don’t mention anything about that, why assume that RTA has a ospf priority of 0?

Q7 is so easy, and A, B, C are clearly wrong as well.

About Q9, clearly A. Output states on DEV3 that the ospf priority of DEV1 is 2. 2 > 1…. hence…. A! Or am I overlooking something in this pretty easy question?

This is how things should look on a BDR:

B#sh ip ospf nei

Neighbor ID Pri State Dead Time Address Interface
10.0.0.1 0 FULL/DROTHER 00:00:30 10.0.0.1 FastEthernet1/0
10.0.0.3 1 FULL/DR 00:00:36 10.0.0.3 FastEthernet1/0

BDR is ALWAYS in FULL state with DROTHER!

Q7
A, B wrong
the output could only be generated ONLY if RTA and RTC are DROTHER
D is wrong because if RTA would be BDR it would have FULL with both RTB and RTC
C is wrong because two DROTHER routers do NOT exchange LSAs. LSAs are exchanged ONLY with DR and BDR.
— in the end there is NO correct answer ?!?!?

@digitaltut,

probably a typo in Q5 B -> “missing the subnetS”, not subnet.

Thanks for this web, btw.

Q 6
guys simply , the network command is for advertising the subnet and send hello in that interface being participating in ospf ok
so i say A & B are correct ,,, Why?
cuz passive interfaces will neither send hello nor receive from RTB and thus no adjacency is formed beetween ,, but it will still help in the routing process BY advertising that subnet ok
we use this command when we have e.g. router connected to L2 switch , so we don’t want to send hello in that interface but we still want to advertise that network
close the discussion about Q6
(and there is misconfiguring in f0/1 , it’s suppose to be 10.10.10.129/25 )

cheeers , WALLAHI (swear) i really love this site and all folks in contributing

for Q 7
in the begging i was thinking that all answers are not correct like many of you
but then i saw one of the comments saying 12 seconds and might be still exchanging
so i tried that in GNS3 and i really really thing that D is correct
you see
when two neighbors become adjacent they go through 4 phases
1- 2way/DROther 2- EXSTART/DROther 3- EXSTART/DRorBDRorDROther
4- Full/DRorBDRorDROther ,,,,,, are you guys catching up
so the only time they get through the phase 2way/drother is if there is election
i think they are in the pre-election phase when this snapshot was taken …….
and i think the hello timer was set to 5seconds “ip ospf hello-timer 5″

anyway i don’t see any other answer but D , am sure there is a mistake in the picture
as there is a mistake in Q6 picture too

and how in heck they are in one subnet but each coming from different interface !!!!!!!!
and in one subnet 10.0.0/24

Answer for Question 7 is correct ,,,,,

You can see RTC is priority 0 its mean it will not participate in DR/BDR election.
And RTB is showing DR with RTA

So now RTA has the ability to become a DR

Q8.
Agree with answer E but disagree with with the explanation: you don’t know RTD’s priority.
So:
Either RTD’s priority is 1 or more and then in that case RTD is the DR and so answer E is correct.
Either RTD’s priority is 0 and then in that case it is DRother. Nevertheless the adjacency to RTC will still be in FULL/BDR.

Q7

I have tried this scenario in GNS3 and conclude that actually all the answers are wrong

2Way/DROTHERS means that RTA can’t be a BDR have a priority of 0 too as RTC

For RTA to be a BDR the result of it should have Full/DROTHERS with RTC.

Q7

I have tried this scenario in GNS3 and conclude that actually all the answers are wrong

2Way/DROTHERS means that RTA can’t be a BDR have a priority of 0 too as RTC

For RTA to be a BDR it should have Full/DROTHERS with RTC.

Q7)

First All routers will form Full relationship with DR and BDR. From the output shown show ip ospf neighbor, we can see it only formed 2-way relation with RTC.

Best answer I can think of is B.

As higher IP address has to be chosen in DR selection, but 192.168.45.2 is not selected as DR. This is not the right Answer but most suitable. Please correct me.I love to be corrected

Q7)
First All routers will form Full relationship with DR and BDR. From the output shown show ip ospf neighbor, we can see it only formed 2-way relation with RTC.
Best answer I can think of is B.
As higher IP address has to be chosen in DR selection, but 192.168.45.2 is not selected as DR. This is not the right Answer but most suitable. Please correct me.

@ Ron

B. Neighbor 192.168.45.1 has changed its OSPF priority number.

The ip address of the answer is .1 not .2 the priority is 1 so it was never changed.

This is not the correct answer.

The only possible answer I think is correct is D, when the priority on RTA was just change from 0 to 1 but the OSPF process was not cleared so it will have 2way/drother and Full/DR and that is how this will fit into the picture.

Please comment on this
Thanks

Q6, I am not understand could u any one explain. in that question The discussion about passive interface but in dispaly configuration passive interface was not configured as well OSPF also not configured.

This was so much helpful; thanks for posting

plz send me latest dumps.i m preparing of route .
send me dumps link plz

Q7]
why ( C. Router RTA and neighbor 192.168.45.2 are exchanging OSPF LSAs. ) is a wrong answer?

Q7

why are the neighbors coming from different interfaces?

Question 1, 8 , 10 in my exam today. Valid answers.