OSPF Questions 7
Here you will find answers to OSPF Questions – Part 7
Question 1
Refer to the exhibit. ROUTE.com is planning to implement a new secure OSPF network to support traffic between clients on the 172.16.10.0/24 network and the file server on the 172.16.20.0/24 network. You have been asked to review the implementation plan for the OSPF project.
Which statement about the plan is true?
A. It is complete as written.
B. It should include a task that shuts down all unused interfaces.
C. It should include tasks that enable and verify OSPF authentication.
D. It should include a task that establishes a file transfer baseline before and after the configuration is changed.
Answer: C
Explanation
The complete implementation plan should be
1. Enable OSPF process 1 on all routers
2. Enable area 0 on R2, R3 and R4
3. Enable area 10 on R1, R2 and R3
4. Enable area 20 on R4 and R5
5. Enable and verify OSPF authentication
6. Verify that all routers contain a complete routing table
7. Verify that the clients can successfully access the server
8. Document configuration changes
Question 2
Refer to the exhibit. ROUTE.com is planning to implement a secure OSPF network to support traffic between clients on the 172.16.10.0/24 network and the file server on the 172.16.20.0/24 network. You have been asked to review the implementation and verification plans.
Which statement about the plan is true?
A. It is complete as written.
B. It should include a task that verifies that the interarea routes are using the proper MED.
C. The plan should include a task that verifies that load sharing is active on the appropriate links.
D. The plan should include a task that verifies end-to-end connectivity between the clients and the file server.
Answer: D
Question 3
Refer to the exhibit. ROUTE.com is planning to implement a secure OSPF network to support traffic between clients on the 172.16.10.0/24 network and the file server on the 172.16.20.0/24 network. You have been asked to review the implementation and verification plans for this OSPF project.
Which statement about the plan is true?
A. It is complete as written.
B. It should include a task that verifies that the interarea routes are using the proper MED.
C. it should include a task that verifies that load sharing is active on R1 and R4.
D. It should include a task that verifies that all redundant links will become active when the primary links are shut down.
Answer: D
Question 4
Refer to the exhibit. Which two Cisco IOS commands on R2 would verify its OSPF neighbor relationships? (Choose two)
A. show ip ospf
B. show ip ospf interface
C. show ip ospf neighbor
D. show ip ospf database
E. show ip ospf statistics
F. show running-config | begin router ospf
Answer: B C
Explanation
The show ip ospf interface command shows us information about the neighbor count and adjacent neighbor count:
The show ip ospf neighbor command shows us the role of each neighbor (DR, BDR, DROTHER).
Question 5
Which command displays the number of times that the OSPF Shortest Path First (SPF) algorithm has been executed?
A. show ip protocol
B. show ip ospf interface
C. show ip ospf
D. show ip ospf database
Answer: C
Explanation
Below is the output of this command:
Question 6
Refer to the exhibit. Will redistributed RIP routes from OSPF Area 2 be allowed in Area 1?
A. Because Area 1 is an NSSA, redistributed RIP routes will not be allowed.
B. Redistributed RIP routes will be allowed in Area 1 because they will be changed into type 5 LSAs in Area 0 and passed on into Area 1.
C. Because NSSA will discard type 7 LSAs, redistributed RIP routes will not be allowed in Area 1.
D. Redistributed RIP routes will be allowed in Area 1 because they will be changed into type 7 LSAs in Area 0 and passed on into Area 1.
E. RIP routes will be allowed in Area 1 only if they are first redistributed into EIGRP.
Answer: A
Explanation
Area 1 is a NSSA so we can inject EIGRP routes into this area with Type 7 LSAs. Notice that Type 7 LSAs can only be existed in a NSSA. The NSSA ABR of area 1 must converted it into LSA Type 5 before flooding to the whole OSPF domain.
When redistribute RIP into area 2, LSA Type 5 will be created an sent through area 0. But a NSSA is an extension of a stub area. The stub area characteristics still exist, which includes no type 5 LSAs allowed.
Note: A stub area only allows LSA Type 1, 2 and 3.
(Reference & good resource: http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094a88.shtml)
Question 7
Refer to the exhibit. OSPF has been configured on all routers in the network and Area 1 has been configured as a NSSA. Which statement is true about the NSSA Area 1?
A. Redistributed RIP and IGRP routes will appear in Area 1. They will be advertised via type 5 LSAs.
B. Only redistributed RIP routes will appear in Area 1. They will be advertised via type 7 LSAs.
C. Only redistributed IGRP routes will appear in Area 1. They will be advertised via type 7 LSAs.
D. No redistributed routes can appear in Area 1, only summary routes.
Answer: C
Explanation
Same explanation of Question 6. Please notice that the IGRP routes are redistributed to NSSA area 1 via LSA Type 7. The NSSA ABR of area 1 will convert it into a LSA Type 5 before flooding to area 0 & area 2.
Question 8
Refer to the exhibit. Based on the command output, what is one reason why no routes from the OSPF neighbor 192.168.0.5 are installed in the IP routing table?
A. R3 will only install routes from the neighbor with the lowest priority (Pri). If routes have the same priority, routes from the neighbor with the lowest IP address are used.
B. R3 did not receive any LSAs from 192.168.0.5.
C. Routes from backup designated routers are never installed in the IP routing table.
D. 192.168.0.5 is a redundant link to 192.168.0.4, and load balancing is not enabled.
Answer: B
Explanation
R3 may not receive any LSAs from neighbor 192.168.0.5 because a distribute-list blocks it. But notice that the LSAs are not filtered out in the LSDB since all routers in an OSPF area must be the same (synchronized).
Question 9
Refer to the exhibit. OSPF is running throughout the network. You want to minimize the propagation of LSAs into and out of Area 1.
Which OSPF feature would best achieve this goal?
A. stub
B. totally stubby
C. NSSA
D. totally NSSA
Answer: D
Explanation
We need to redistribute RIP from R1 to Area 1 so Area 3 cannot be a stub or totally stubby area. To minimize the propagation of LSAs into and out of Area 1 we should configure it as a totally NSSA. Notice that a NSSA allows LSA Type 3 & 7 while a Totally NSSA only allows LSA Type 7
Note:
Both Totally Stubby Area & Totally Stubby NSSA do not accept external AS routes or inter-area routes (LSA Types 3, 4 and 5). They recognize only intra-area routes and the default route 0.0.0.0. The main difference between them is Totally Stubby NSSA accepts routes from other AS while Totally Stubby Area does not.
Below summarizes the LSA Types allowed and not allowed in area types:
| Area Type | Type 1 & 2 (within area) | Type 3 (from other areas) | Type 4 | Type 5 | Type 7 |
| Standard & backbone | Yes | Yes | Yes | Yes | No |
| Stub | Yes | Yes | No | No | No |
| Totally stubby | Yes | No | No | No | No |
| NSSA | Yes | Yes | No | No | Yes |
| Totally (stubby) NSSA | Yes | No | No | No | Yes |
Question 10
Refer to the exhibit. A company would prefer all Internet-bound OSPF routed traffic to use ISP ABC with ISP DEF as a backup. As the network consultant, what three configuration changes might you make? (Choose three)
A. The default-information originate command should be configured on router B1 and B4.
B. The default-information originate command should be configured on router B2 and B3.
C. If the metric value for ISP ABC is set at the default, the ISP DEF metric value should be set to 1.
D. If the metric value for ISP ABC is set at the default, the ISP DEF metric value should be set to 25.
E. The metric type value should be set to type 1.
F. The metric type value should be set to type 2.
Answer: B D F
Explanation
Routers B2 & B3 need to advertise a default route to the Internet for “inside” OSPF routers so we should use the “default-information originate” command with a default route (something like “ip route 0.0.0.0 0.0.0.0
If no metric is specified, OSPF puts a default value of 20 when redistributing routes from all protocols except BGP routes (BGP routes get a metric of 1). We use ISP DEF as a backup so its metric value should be set to a higher value than 20 -> D is correct.
There are two types of external routes: external type 1 and external type 2. The difference between the two is in the way the cost (metric) of the route is being calculated:
+ The cost of a type 2 route is always the external cost, irrespective of the interior cost to reach that route.
+ Type 1 cost is the addition of the external cost and the internal cost used to reach that route.
-> We should configure the type 2 external route to make sure the ISP ABC is always referred over ISP DEF because internal routing does not determine the path.
Note: E2 is the default external metric, but E1 is preferred over E2 if two equal-cost paths exist.
Question 11
Refer to the exhibit. A network administrator wants to reduce the number of OSPF routes advertised from Area 1 into Area 2. As the router configuration specialist, what two things would you do to accomplish this goal? (Choose two)
A. Enter the configuration on router B1.
B. Enter the configuration on router B4.
C. On the same router, enter the Summary-address 10.10.1.0 255.255.255.128 subcommand.
D. On the same router, enter the Area 1 range 10.10.1.0 255.255.255.128 subcommand.
E. On the same router, enter the Area 2 range 10.10.1.0 255.255.255.128 subcommand.
Answer: A D
These are new questions.
I think the answers provided for Q11 are wrong…?
Correct Options should be:
a. Enter the configuration on router B1.
b. Enter the configuration on router B4.
c. On the same router, enter the Summary-address 10.10.1.0 255.255.255.128 subcommand.
d. On the same router, enter the Area 1 range 10.10.1.0 255.255.255.128 subcommand.
e. On the same router, enter the Area 2 range 10.10.1.0 255.255.255.128 subcommand.
With the corect Answers being: A D
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!
Correct answers for Question 11 is A and D
For Q11.
network administrator wants to reduce the number of OSPF routes advertised from Area 1 into Area 2.
By entering Default information originate in B1 and B4 how inter area router get summarized. (From Area 1 to Area 2). It’s achived by through Inter area route -summarization or making area 2 as a Totally stubby.
Can someone elaborate on Question 11. I don’t understand it.
guys which website can i use for switch
Q11.
How is answer D going to reduce the routes going from area A to B??? ISPs ABC and DEF are not mentioned nor implied in the original question. Besides that, changing the metric-type to prefer one ISP over the other is NOT going to reduce routes going into area B, unless there are fewer routes to be advertised from ISP DEF.
Is this going to be on the test?
Sorry, I meant to say “changing the metric value…”
Question 11,
How is the answer A and D? The point of the question is to reduce advertisement from area 1 to area 2, wouldn’t you to summarize the routes or distribute the routes to filter?
Please explain. Thanks.
@All: Thanks for your detection. I updated the answers on Question 11.
Q10;
E1 is preferred over E2 according to Cisco, why would we choose E2 for the metric ? Could someone explain? Thanks.
Wait, did I miss stoimheng? What was causing the routing instability (path changes according to traceroute)?Running a non-backbone area isn’t super-unusual, especially if you have lots of sites that might get bolted together with stoimheng later.I have one customer running lots of OSPF areas, and no Area 0. All of those different areas are present on a couple of core switches, but without an Area 0, those switches aren’t ABRs. Instead, the areas are all bolted together with redistribution into and out of EIGRP. Sigh.
@johncc42: if we have E2, it ensures that we always have a better route via ISP ABC (metric 20), whereas ISP DEF will always have a metric of 25. If we use E1 there are might be cases for some routers where ISP DEF has lower metric than ISP ABC (possible example is R3). plz smbd correct me, if i am wrong.
Q10 I did a little research because it was confusing to me why you would use area range instead of summary-address; well here is the reason why.
The “Area range” command ONLY summarizes LSA type 1s and it must be
configured on the ABR, whereas, the “Summary-address” command summarizes LSA
type 5s and 7s.
To summarize LSA type 5s and 7s you can configured the “summary-address”
command on the ASBR. If you are summarizing LSA type 7s, then you can
configure the “summary-address” on the ASBR or the ABR of that NSSA area.
Q11 I did a little research because it was confusing to me why you would use area range instead of summary-address; well here is the reason why.
The “Area range” command ONLY summarizes LSA type 1s and it must be
configured on the ABR, whereas, the “Summary-address” command summarizes LSA
type 5s and 7s.
To summarize LSA type 5s and 7s you can configured the “summary-address”
command on the ASBR. If you are summarizing LSA type 7s, then you can
configure the “summary-address” on the ASBR or the ABR of that NSSA area.
Bishop, there are no type 5 of 7 LSA’s no Q11 so no need to use summary -address.
Explantion “R3 may not receive any LSAs from neighbor 192.168.0.5 because a distribute-list blocks it.” Can any one explains it…
I think as neighbor 192.168.0.5 is actually BDR and answer bdr routes are not installed in routing table, is correct, beacuse all routes will come from DR. and the answer that no lsa are received from 192.168.0.5 is correct as well beacuse DR would sent lsa not bda…
Can any one please confirm, am i thinking on right lines
Q2:
isn’t “end-to-end connectivity between the clients and the file server ” (choice E)
is already verified when we had the extended ping in the first point in the plan?
Amira,
I think so too
Amira,
The pings between the two routers would test connectivity between the two networks. But if the clients and/or the file server were configured with the wrong default gateway, then end-to-end connectivity would fail.
the site was down for few moments. we cant effort that
Hi,
I don´t understand Q8.
In my opinion this answer must be correct, isn´t it?
C. Routes from backup designated routers are never installed in the IP routing table.
Question 8 May 6th, 2012 —> You are right
Q8 June 29th, 2012 —-> You are almost right
LSAs are always received from the DR and not from de BDR —> B is right (it has nothing to do with distribute lists)
When the DR fails, the BDR takes over the control so now its routes are installed in the other routers’ routing tables —> C is wrong —> It is a tricky answer because now it is actually the DR and not the BDR
Regards
Question 8.
Number D seems like the correct Answer. R3 formed a full ajdacency with 192.168.0.5. At minimum it must have received atleast one LSA for the directly connected network. Besides LSA do not determine what gets put into the routing table. It is the SPF algorithm that does that. I think load balancing is disabled using the maximum-paths OSPF command or 192.168.0.5 just has higher cost paths.
@ffar
I agree unless someone else can explain. Thank you!
Did a little research? :P I’d have said “I studied the CCNP ROUTE material” instead :D.
Q11 is indeed A and D.
summary-address –> only on ASBRs
area range –> only Inter-Area
Of course on B1 (A), since you want to summarize from Area 1 — >, so this will need to be done on an ABR of area 1.
And of course area 1 range….. since you summarize routes from that area. It’s really the most simple question.
I’m 100% sure D is the correct answer.
like ffar said, answer B can’t be right: R3 did not receive any LSAs from 192.168.0.5.
because At minimum R3 must have received atleast one LSA for the directly connected network..
Digitaltut what is the correct answer for the test? B?
Question 3 was in my test!
Q8.
This question is so badly written.
First what does it mean?
Is it:
a) why is there no route whose next-hop is 116.16.35.5?
or is it:
b) why is there no route to 192.168.0.5/32?
Secondly in OSPF you don’t receive routes from neighbors : you receive LSA which describe the topology of the area, then you run SPF which may or not decide that some OSPF neighbor is a next-hop for a specific prefix. Finally you may (but it would be a really weird decision …) decide to not install the route in the routing table using filtering.
That said, the right answer for question a) should be “SPF didn’t elect 116.16.35.5 as a next-hop for some prefix or it did but it got filtered.”
If we consider load-balancing was disabled (maximum-paths 1) we could complete this answer:
“SPF didn’t elect 116.16.35.5 as a next-hop for some prefix or it did but it got filtered or it was a second equal-cost path”
The right answer for question b) could be :
“Router 192.168.0.5 is simply not including its loopback address in its LSA -> ‘network 192.168.0.5 0.0.0.0′ is missing in its configuration”
We can also eliminate the answers one by one:
A is wrong: priority has nothing to do with installing routes or not. Priority isused to elect DR and DR on broadcast networks. Also the “prioritiness” is not an attribute of a route but of a router.
B is wrong: 192.168.0.5 generated at least an Type-1 LSA which was flooded inside the area and in the end was received by R3.
C is wrong: Again OSPF doesn’t advertise routes but LSA. Also a BDR (or even a DRother router) can be a valid next-hop for some prefix if SPF decides it is the shortest path.
D is wrong: 192.168.0.5 and 192.168.0.4 are too very distinct routers.
Q8.
This question is so badly written.
First what does it mean?
Is it:
a) why is there no route whose next-hop is 116.16.35.5?
or is it:
b) why is there no route to 192.168.0.5/32?
Secondly in OSPF you don’t receive routes from neighbors : you receive LSA which describe the topology of the area, then you run SPF which may or not decide that some OSPF neighbor is a next-hop for a specific prefix. Finally you may (but it would be a really weird decision …) decide to not install the route in the routing table using filtering.
That said, the right answer for question a) should be “SPF didn’t elect 116.16.35.5 as a next-hop for some prefix or it did but it got filtered.”
If we consider load-balancing was disabled (maximum-paths 1) we could complete this answer:
“SPF didn’t elect 116.16.35.5 as a next-hop for some prefix or it did but it got filtered or it was a second equal-cost path”
The right answer for question b) could be :
“Router 192.168.0.5 is simply not including its loopback address in its LSA -> ‘network 192.168.0.5 0.0.0.0′ is missing in its configuration”
or
“Prefix 192.168.0.5/32 was filtered and thus not installed in the routing table”
We can also eliminate the answers one by one:
A is wrong: priority has nothing to do with installing routes or not. Priority isused to elect DR and DR on broadcast networks. Also the “prioritiness” is not an attribute of a route but of a router.
B is wrong: 192.168.0.5 generated at least an Type-1 LSA which was flooded inside the area and in the end was received by R3.
C is wrong: Again OSPF doesn’t advertise routes but LSA. Also a BDR (or even a DRother router) can be a valid next-hop for some prefix if SPF decides it is the shortest path.
D is wrong: 192.168.0.5 and 192.168.0.4 are too very distinct routers.
Q6 NSSA allows Type 1,2,3 and type 7 and Answer D is the correct one.
T-NSSA allows Type 1,2 and 7
Stub allows type 1,2 and 3
T-stub allows type 1 and 2 only.
Q11
Its a wrong subnet in N1, N6, N7 network 10.10.1.64/24 instead 10.10.1.64/28.
@ Pedro
All correct just 1 thing I believe is not write and it is(correct me if I am wrong please) :
“B is wrong: 192.168.0.5 generated at least an Type-1 LSA which was flooded inside the area and in the end was received by R3.”
Since 192.168.0.5 is the BDR and R3 will receive LSAs from only DR then it will not receive LSAs from 192.168.0.5. The LSAs in the multiaccess broadcast networks are flooded to 224.0.0.6 which only DR and BDR receive on.
Seems to me only answer B is correct here. It is not a direct correct answer to the question but it is the only true statement listed.
Please comment.
Q8
A normal router (i.e. R1 – on Ethernet segment) sends on 224.0.0.6 to DR and BDR but DR sends to others on 224.0.0.5. It seems that BDR sends type 1 LSA (router) only to 224.0.0.6 (so R1 will not receive type 1 LSA from BDR cause he ignores LSA address to 225.0.0.6). BDR sends all his LSA only to DR.
So B is correct
Question 9
Refer to the exhibit. OSPF is running throughout the network. You want to minimize the propagation of LSAs into and out of Area 1.
Which OSPF feature would best achieve this goal?
A. stub
B. totally stubby
C. NSSA
D. totally NSSA
Answer: B
Question 2 seems off…
the first step was basically verifying end to end connectivity… I would have thought that verify load balancing was a better option…
Question 2
ping in first step achive the end to end connectivity
@Scotridge :::
Question NO 9 Digitultut’s Answer D is Correct. Because
External RIP routes are being routed in OSPF area 1 where they are injected as type 7 so we use Stub NSSA on the ASBR(R2) and Stub on R3 and R4.
@Scotridge :::
PLz donot consider my upper post :::
Question NO 9 Digitultut’s Answer D is Correct. Because
External RIP routes are being routed in OSPF area 1 where they are injected as type 7 so we use (area 1 NSSA) command on the ASBR(R2) and
(Area 1 NSSA no-summary) command on R3 and R4.
you can verify issuing the command “show ip ospf database” and you will see the type 7 lsa’s on ASBR(R2) and LSA’s Type 5 and 7 on both the ABR routers(R3 ,R4)..
Q8
Answer B: R3 did not receive any LSAs from 192.168.0.5.
How can R3 be fully adjacent with the router RID 192.168.0.5 without having received any LSA? R3 received at least 192.168.0.5 LSA1 no ?
Please comment, this question is so tricky…
Q8 again…
AC are wrong ok.
I think B is wrong too (see my comment below)
It leaves us with answer D: 192.168.0.5 is a redundant link to 192.168.0.4, and load balancing is not enabled.
–> If 192.168.0.5 is a redundant link to 192.168.0.4 and OSPF maximum-paths is set to 1 (load balancing not enabled) that could explain why no routes from 192.168.0.5 are added to the routing table.
R3 would have two LSA3 to reach each IA network in its LSDB but with maximum-paths set to 1, R3 will use the first LSA3s it finds in its LSDB to add the route the routing table. As 192.168.0.4 is the DR and 192.168.0.5 the BDR (and ospf priority are the same), we can assume that 192.168.0.4 was switched on before 192.168.0.5, thus that R3 has received 192.168.0.4′s LSA3 first.
In that scenario, R3 would only have routes from 192.168.0.4 for those IA network making the right answer D not B.
Please comment.
Hello,
Is someone could explain me the question 10 ? I do not understand why we have to use E2 and not E1 metric-type in this scenario? Moreover I do not understand why “If the metric value for ISP ABC is set at the default, the ISP DEF metric value should be set to 25). Thanks for your help.
By the way than you digitaltut for this great website fullfill of so valuable information !
Q2. I believe the key words would be “implement a secure OSPF network” we must take care of the OSPF network and not the default gateway the hosts might have, therefore if we have already checked it on step 1, the correct answer should be “A. It is complete as written.”
@o2
By default, when using a type 2 metric, the internal cost to reach the ASBRs (B2 and B3 routers in this case) is not taken into consideration. If a type 1 metric should be used for this default route, then for example router N1 could have a lower cost path to the default route advertised by B3, and we don’t want that. We want to take the path to B2, and then to ISP ABC.
Also, here is some helpful information about the default route metric in OSPF :
http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a00801ec9f0.shtml
I believe that the explanation from Q10 is incorrect regarding the metric. All default route metric is set to 1, not 20 unless configured in the “default-information originate” command, with the “metric” parameter.
Only when redistributing from other protocols (except BGP) is the default cost set to 20. The default route is an exception to this rule.