CCNA – OSPF Questions
Here you will find answers to OSPF Questions
Note: If you are not sure about OSPF, please read my OSPF tutorial
Question 1
Which of the following statements below best describe the process identifier that is used to run OSPF on a router? (Choose two)
A – It is an optional parameter required only if multiple OSPF processes are running on the router
B – It is locally significant
C – It is needed to identify a unique instance of an OSPF database
D – All routers in the same OSPF area must have the same process ID if they are to exchange routing information
Answer: B C
Question 2:
Why R1 can’t establish an OSPF neighbor relationship with R3 according to the following graphic? (Choose two)
A – Configure EIGRP on these routers with a lower administrative distance
B – All routers should be configured for backbone Area 1
C – R1 and R3 have been configured in different areas
D – The hello and dead interval timers are not configured the same values on R1 and R3
Answer: C D
Explanation:
A is not correct because configure EIGRP on these routers (with a lower administrative distance) will force these routers to run EIGRP, not OSPF.
B is not correct because the backbone area of OSPF is always Area 0.
C and D are correct because these entries must match on neighboring routers:
- Hello and dead intervals
– Area ID (Area 0 in this case)
– Authentication password
– Stub area flag
Question 3:
Which items are correct about the routing protocol OSPF? (Choose three)
A – Support VLSM
B – Increase routing overhead on the network
C – Confine network instability to one area of the network
D – Allow extensive control of routing updates
Answer: A C D
Explanation:
Routing overhead is the amount of information needed to describe the changes in a dynamic network topology. All routers in an OSPF area have identical copies of the topology database and the topology database of one area is hidden from the rest of the areas to reduce routing overhead because fewer routing updates are sent and smaller routing trees are computed and maintained (allow extensive control of routing updates and confine network instability to one area of the network).
Question 4:
Which three features are of OSPF routing protocol? (Choose three)
A – Converge quickly
B – OSPF is a classful routing protocol
C – Identify the best route by use of cost
D – Before exchanging routing information, OSPF routers find out neighbors
Answer: A C D
Question 5:
OSPF routing uses the concept of areas. What are the characteristics of OSPF areas? (Chose three)
A – Each OSPF area requires a loopback interface to be configured
B – Areas may be assigned any number from 0 to 65535
C – Area 0 is called the backbone area
D – Hierarchical OSPF networks do not require multiple areas
E – Multiple OSPF areas must connect to area 0
F – Single area OSPF networks must be configured in area 1
Answer: B C E
Explanation:
I used to think the answers should be C D E and here is my explanation:
OSPF can use an active interface for its router ID, so a loopback interface is not a must -> A is incorrect.
OSPF Area is a 32-bit number so we can use up to 232 – 1 = 4294967296 – 1 (since Area 0 is the first area). Remember that only process ID is a 16-bit number and ranges from 1 to 65535 -> B is incorrect.
F is incorrect too because single area OSPF netwoks must be configured in Area 0, which is called the backbone area.
For answer D, it is a bit hard to guess what they want to say about “hierarchical” but we should understand “Hierarchical OSPF networks” as “OSPF networks”. D is correct bercause we can only have one area (area 0 – the backbone area) for our networks.
But TT commented on 01-11-2010:
Especially to note on choice B, D, and E:
Choice B: we all know that The areas can be any number from 0 to 4.2 billion and 1 to 65,535 for the Process ID. As choice B specifies ‘area’ (be aware, it’s not saying ‘process id), there is no reason to say that we cannot assign numbers from 0 to 65535 for area # (it is using ‘may be’, not ‘have to be’ or ‘ought to be’). Hence, we do not worry about assigning ’0′.
Choice E: as Area 0 is the backbone, we all understand that any areas in a OSPF network have to be connected to it. And actually this is implicitly saying that multiple areas form a hierarchical OSPF network, as Area 0 being a root and others being its leaves.
Choice D: when it specifies ‘Hierarchical’, at least 2 areas should be required to form such topology (of course that includes Area 0)
Although Choice B is not an absolutely accurate statement since it not only can be assigned up to 65535, it is still a correct answer. And again, it specifies ‘area’, not ‘process id’, so ’0′ can be included. Finally, it would be meaningless to call OSPF a hierarchical network if no more than one area is present.
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I reviewed the question and think it is a more suitable solution with choice B than choice D, surely it is a tricky question!
Question 6:
Part of the OSPF network is shown below:
Configuration exhibit:
R1 routing commands:
ip route 0.0.0.0 0.0.0.0 serial0/0
router ospf 1
network 172.16.100.0 0.0.0.3 area 0
network 172.16.100.64 0.0.0.63 area 0
network 172.16.100.128 0.0.0.31 area 0
default-information originate
You work as a network technician, study the exhibits carefully. Assume that all router interfaces are operational and correctly configured. In addition, assume that OSPF has been correctly configured on router R2. How will the default route configured on R1 affect the operation of R2?
A – Any packet destined for a network that is not directly connected to router R2 will be dropped immediately
B – Any packet destined for a network that is not directly connected to router R1 will be dropped
C – Any packet destined for a network that is not directly connected to router R2 will be dropped immediately because of the lack of a gateway on R1
D – The network directly connected to a router R2 will not be able to communicate with the 172.16.100.0, 172.16.100.28 and 172.16.100.64 subnetworks.
E – Any packet destined for a network that is not referenced in the routing table of router R2 will be directed to R1. R1 will then send that packet back to R2 and a routing loop will occur
Answer: E
Explanation:
First, notice that the more-specific routes will always be favored over less-specific routes regardless of the administrative distance set for a protocol. In this case, because we use OSPF for three networks (172.16.100.0 0.0.0.3, 172.16.100.64 0.0.0.63, 172.16.100.128 0.0.0.31) so the packets destined for these networks will not be affected by the default route.
The default route configured on R1 “ip route 0.0.0.0 0.0.0.0 serial0/0″ will send any packet whose destination network is not referenced in the routing table of router R1 to R2, it doesn’t drop anything so answers A, B and C are not correct. D is not correct too because these routes are declared in R1 and the question says that “OSPF has been correctly configured on router R2″, so network directly connected to router R2 can communicate with those three subnetworks.
As said above, the default route configured on R1 will send any packet destined for a network that is not referenced in its routing table to R2; R2 in turn sends it to R1 because it is the only way and a routing loop will occur.
@Bydlak
The process ID of any OSPF process is locally significant eg it matters to the local router. The process ID in one router has no value in other routers; they too run an OSPF process at some ID, where none of the other routers care for. So the process IDs do not have to match (so D is wrong), and B is correct – the process ID is significant to the local router.
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 you practice the simulation, use packet tracer or gns3. Best wishes to all!
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Regards
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@Ropam, search google for free copy visual certexam, vce engine, that is how i was able to download the dumps, if the copy you have not enabling you to down load the dumps, look for other free copies. Hope this helps!
for #6 I thought the default route referenced the next hop address as opposed to the outbound interface. I have been looking at this like. OK… its saying for all packets that do NOT have routes in the routing table send it to next hop S0/0 which would be the ISP. We are certain I was wrong? Taking the test tomorrow afternoon. Guess i’m gonna take 9tuts word on this one.
@Ciz
with default route u use either the next hop IP address or the routers exit interface …which in this case the exit interface is s0/0 leading to router 2 (R2)
@xallax @9tut
What is process ID? i read 3 pages of your tutorial about OSPF. Never see the process ID there?
now i know what is process id i read it on question 2 explanation
Q2. Can someone explain
C – R1 and R3 have been configured in different areas
R1 and R3 are in the same area according to the graphic? isn’t it
@warfreak
the process id is a unique identifier on the router so that the ospf databases to overlap.
it is similar to what you see in task manager on any windows nt platform under PID (process ID)
regarding Q2… yes, judging from the picture they should both be part of the default network yet they dont form neighboring relationship.
as 9tut pointed out above, they must match the ospf area ID and the timers. by process of elimination you end up with options C and D as correct ones
study study OSFP alot of question was on the exam.. failed by a few points
@xallax thank you so much.
im having trouble with the same question as warfreak ask thanks
no OSPF SIM ???????????
Hi friends! this is a question..
is it mandatory to advertise interface loopback in the ospf routing process to take part in the process of election DR/BDR?
I dont think soo but I need some confirmation!
cheers
Took ICND2 today, pass 916/100. Q6 was on the test. I got it wrong.
What chapter in Odom’s book covers the sharing of default routes? Chapter/page?
can u explain me about the routing loop in the OSPF networks?
Ple explain me about tha routing loop in that network?
I don’t thing so their is loop
I don’t get the answer in Q6 too. If it says any packet not in the routing table, (here I think not even learnt by OSPF) without a default route set to R2 S0/1 the packet will be dropped. Right? Unless I miss something important from the question.
I reread the question again and it looks like it’s a scenario. That is if there’s a default route configured in R2 S0/1, then it’ll route the packet to R1. R1 will route back to R2 knowing there’s no route for it either. Hope that’s what the question and answer mean.
I finally understand Q6. The command “default-information originate” is asking the neighbor R2 to use R1 as the default route. So R2 will send packet to R1 if no match found in R2 routing table. R1 will immediately send the packet back to R2, via S0/0, because of the default route.
I have a question for 9tut..?
Can a single OSPF Area have more than one DR..? If so, in which case..? Plz Explain, thanks
@MalikCCNA: Of course 1 OSPF area can have more than 1 DR. DR/BDR are elected for each segment (a broadcast domain, in most cases), not for 1 area.
“default-information originate” this command leads to what causes on router?
On question 5, one of the answers is that you can assign an Area between 0 and 65535. This is close but not correct. The limit of 65535 as it relates to OSPF is the process ID “router ospf 65535″. The limit on area is like 2000000.
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…q5 on exam..good luck at all…just keeping read andy study…
@SardisKan
Q5 is correct…and got it right…listen to 9tut!!!…
https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-ash3/554728_152456048225950_1461704479_n.jpg
can anyone explain this ? thx
QAnonymous
R3 is fully adjacent with R1 and is the DR for the 10.1.1.0 network.
That is correct because it is fully adjacent (we can see that in statement FULL:) and is DR for network 10.1.1.0 because there are only two routers on this network and the R1 is BDR, conclusion ? R3 must be DR. R3 and R1 are in the same subnet 10.1.1.0 as you can see in the photo.
R3 is fully adjacent with R1 and R2.
As I said previously FULL means they’re fully adjacent
Who encounter Q5? what is the most appropriate RIGHT answer? :-)
@Anonymous @yoy regarding
https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-ash3/554728_152456048225950_1461704479_n.jpg
Also, DR/BDR elections don’t occur on Serial links so that’s why R3 and R2 don’t elect a DR -> all those relevant options are wrong.
You can tell that R1 will be the DR because its interface Fa0/1 has a higher IP. Confirmed since R2 is the BDR.
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
Can anyone explain me about process id?
Hi! , why isnt correct in Q1 ??
All routers in the same OSPF area must have the same process ID if they are to exchange routing information
Pass today with 907 score, please practice VTP and try to answer each question differently because on my test sim few comands did not work one wes Show Vlan, all info you need are here on tiss site.
Am preparing myself for an exam on October 30. Which chapters should I be at my strongest. Help guys thank you.
q6– my notes—default information originate=any packet destined for a network that is not referenced in the routing table of R2 will be directed to R1– notice that this command is on R1–
this happens because R2 obtains a full routing table from R1 — hope this helps someone else– oh yes— R2 finds that R1 has a default route so anything with an unknown destination will be forwarded to R1
q6— previous comments from others– note that this loop occurs and this can happen with many packets — think of the waste of a loop of packets?!— I have run into a loop once — it was an old DOS program running on a windows 95 computer — the loop completely took over the computer — Turned off the computer — reinstalled the registry — found registry recovery instructions — computer returned to normal
q6— default route and default-information originate on the same router caused the loop
q6– advice — look at ospf tutorial on this site — the last section is a bit overwhelming — but the first 2 sections are really good !!!!– you need to understand not memorize
i created the q6 scenario on packet tracer but packet originated frm r1 to unknwn net. gets dropped on r2 . is “default information originate” cmd is enabled by default on real routers .
i will appreciate if i get answer . (riot.deadly@gmail.com)
I’ll give CCNA exam in first week of November..
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Respect 9tut
973 ccna test
I will drop something in the donation jar
I will be back for the CCNA security
The questions are all here
the sims are all still good, VTP,the ACL web server, and the eigrp
don’t stress yourselves out study up and you will do fine
I am an idiot and that is by independent evaluation
if my dumb self can do it you guys are shoe ins
GOOD LUCK
to Rubin’s question from Oct. 3rd, the process id does NOT have to match for routes to be discovered in OSPF, the area id MUST match though. The process id is just a locally significant numeric value.
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I think one of a basic good resources is
http://ipcisco.com/single-area-ospf-configuration/
about OSPF..And more;)