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.
—————————————————————————————————-
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.
xallax
can dead timers in ospf be configured?
@stantheman
sure it can, but that’s not a problem for us at the CCNA leve
read here:
http://www.cisco.com/en/US/docs/ios/12_0s/feature/guide/fasthelo.html
Here are the dumps:
D => Discover Your Knowledge First
U => Unite Your Thoughts
M => Manage, Mix and Match
P => Provide Prohibited Questions
S => Start, Energize and Progress
hi i am taking my ccna xam next week,cud anybdy say if the dunps changed and the latest sims givn in the recent exams???????
@ anyone can u send me the latest CCNA actual exam?
please send it to sab3001@hotmail.com
Appreciate anyone who will share it. Thanks!
@Claudio from Chile:
Why 2 routers can not form a adjacency?:
A) the dead timers intervale are diferents in both routers.
B) ID process are diferents in both routers.
The reason B is not the answer is because in OSPF the process ID is locally significant. You can have different process IDs throughout the routers what you can’t have is different areas ie:
R1: ip add 192.168.0.0 0.0.255.255 area 0
R2: ip add 10.10.0.0 0.0.255.255 area 1
Those two routers will not exchange topologies without you setting up a border router.
Just an FYI:
In EIGRP the AS (Autonomus System) does have to match for routers to share their topolgies.
hey guys i heard tat dumbs has been changed is it true????
yes . that’s true
Hey i am giving the exam on 21st of sep.
What kind of questions are changed??
Pls tell me..I dont have enough days,….
Are the sims changed??
Q6.
General question about “Default Route”, also referred to as gateway of last resort. This routes handles packets which does not reference any route in the routing table. Mostly used for internet based traffic.
My question is how should the default route be configured to avoid loop, on question 6?
Anyone share some light on this? Thanks.
@koffy
correct configuration:
ip route 0.0.0.0 0.0.0.0 serial0/1
the default route should be towards the ISP router
Thanks xallax. That’s what I thought initially.
default-information originate : this command will make the default gateway of R2 as R1
anyone please send me the latest dumps to ponyango19@yahoo.com..thanx
Taking exam in sept.any one with latest dumps.emeka062004@yahoo.co.uk
Taking the exam in sept,Anyone with latest dumpd.
emeka062004@yahoo.co.uk
default-information originate: Can some of you explain a bit more in depth PLEASE!!!!
OK, I can’t follow question 2. It asks Why R1 can’t establish a neighbor relationship with R3 but doesn’t give you the configuration. How would you answer that without seeing the configuration. What am I missing?
OK, the light just went on! I figured it out. It’s actually asking what are 2 possible reasons that R1 can’t estabish a neighbor relationship with r3. Got it!
hi i would just like to know if you don’t save youre config in your sim do you lose all your points there ?
I am going to sit 640-802
Hi Guys
I’M taking my CCNA exam on oct 3, 2011, please help with latest dumps
this is my email Address : risdiholic@yahoo.co.id
many many thanks!
hi guys am taking my exam nov please help me latest dumps
my email kanini.jeniffer@yahoo.com
thanks in advance
@paul
yes for sure.
@BMW
“default-information originate” in OSPF means “To generate a default external route into an OSPF routing domain”.
OMG i would have ace that test
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
Comment: Why should Cisco come up with such unnecessary questions. Is it a way to fail people and make look harder than it is?! There are many ways to test peoples knowledge than tricking with “Areas may be assigned any number from 0 to 65535″. This is my opinion anyway.
Hello Guys I need your invaluable input for the following question…. the question can be found easily if you searching it on the web.
QUESTION 226
Refer to the exhibit. Assume that all of the router interfaces are operational and configured correctly. How will router R2 be affected by the configuration of R1 that is shown in the exhibit?
My question: The answer was alternative A. But why can’t the routers form adjacency with each other. I have built the scenario on packet-tracer and tested it, and the answer is definetively not A. And there no explanations to why?? HELP!!!
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
b, c and e
but the B is bad because the area id can be from 0 to 4.2 billions
The process Id can be from 1 to 65535
I’m wrong?
+ what makes ospf hierachical is the ability to used areas, so question D is wrong too… I’m so confuse..
@liss
read the explanations above please, thank you
@xallax
Q6.
This is just an observation. Please, just hear me out.
The question reads: How will the default route configured on R1 affect the operation of R2.
There is no default route configured on R1. The default route configured is rather on the ISP router S0/0……(R1 S0/1-gateway of last resort).
Would you consider the question as a tard misleading? Like i said, this is just an observation. Thanks.
Q 6
different version of this question :
A router R2 will not form neighbor relationship with R1
B rouer R2 will obtain a full routing table, including a default rotuer, from R1
C R2 will obtain OSPF updates from R1, but will not obtain default router from R1
D R2 will not have a route for the directly connected serial network, but all other directly connected networks will be present, as well the two Ethernet networks connected to R1
Answer is A
The main problem is route loop. my question is why would a loop cause OSPF not forming neighbor ?
@koffy
well, it doesnt really matter where the default route is configured as long as it is distributed to the other routers.
so yes, if it was configured on the ISP router and the ISP router was operating in the same OSPF area as the network routers and the default-information-originate command was enabled, then R1 and R2 would have the ISP router as their gateway of last resort
@nc
are you sure the answer there isnt B?
@xallax
Thanks.
So basically to avoid a loop, we need to include the ISP router in the same OSPF area as the network routers and enable the default-information-originate command. But doesn’t the oval shape that embodied the topology with OSPF area 0 written at the top include the ISP router. Or maybe we need to see the routing table and possible few more information. Thanks.
@koffy
it depends how that default route is set too or you could end up having a routing loop between the ISP router and R1.
@xallax
Thanks. I think we had this discussion once before, few weeks back. Much clearer now.
I am confused about the command default-information originate. What is the purpose of this command? Why is it used? I was looking for a good explanation and I cant find it.
I am going to try Sem 3 of cisco web site.
cisco web::: default information originate (ospf) — to generate external route into ospf routing domain
Question 6) THe default route is to itself. THerefore, when R2 gets it. it says “Oh Its me!” then does nothing. This causes the packets thats not connected to R2 to be dropped as there is no default route in the table. Consider A.
@digitut
OK, now were are getting into semantics here. You say “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’). “ – and I see where you are coming from. However, this is the reason why people come in droves to these sites – because they failed the test the first time and want to know “WHY THE HELL DID I FAIL??” The reason is simple, cisco wants your money. They throw stupid questions that trick you so that you come back for more blood later. This is more of a grammer question that a CCNA question. I am a CCNP/CCIP and aspiring to be a R/S guy soon, and just want to tell everyone this – once you get past CCNP, this crap seems to go away. So, just drudge through it for now and the promiseland awaits. Good Luck to all!!
Hi Guys,
Any one from here can help me for my CCNA exam nextweek.Hope you can send me a latest dump. Thank you so much.. please send it to my mail bcmanahan@gmail.com
@9tut:
In explanation of question 6, I believe there is a typo.
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 R2 to R1……..
And then the other line says:
As said above, the default route configured on R1 will send any packet destined for a network that is not referenced in its (R1′s) routing table to R2….
So, what I am saying is that the first paragraph should be like this:
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……..
Thanks!!
Can some body send me latest dumps? I’ii really appeciate it.
amjadstocks@gmail.com
Thanks
@Nash D: Yes, thanks for your detection. I updated it!
hiiiiiiiii every body
am going2 do my ccna exam next week can u send me last dumps please
salah_ono11@hotmail.com
thanks alot
Plzzzzz friends send me latest CCNA dumps..
Also suggest me some materials from which I can prepare myself for CCNA exam..
my email address: m.aasif.khan@hotmail.com
@ xallax , @anyonelse
Just Wanna confirm if the 1 in the router ospf command means that router interface is enable for and part of area 1? And would that not mean it will fail to form any neighbor adjacency with the other routers in the Area 0 ?
@aryanking
“router ospf 1″ means that you are entering setup mode for the ospf process with the number of 1 on this router.
you have to further configure the router to make it a part of an area
Plzzzzz friends send me latest CCNA dumps..
Also suggest me some materials from which I can prepare myself for CCNA exam..
my email: mwamwaya@yahoo.com