CCNP Route FAQ: OSPF Route Summarization, Filtering, and Default Routing
Q1. Router B1, an internal router in area 1, displays the following output. The only two ABRs connected to area 1 are performing Type 3 LSA filtering. Which of the following answers is true based on the information in the output from B1?
R1# show ip route 10.1.0.0 255.255.0.0 longer-prefixes ! Legend lines omitted for brevity 10.0.0.0/8 is variably subnetted, 17 subnets, 3 masks O 10.1.2.0/24 [110/658] via 10.10.13.1, 00:00:32, Serial0/0/0.1 O IA 10.1.1.0/24 [110/658] via 10.10.23.2, 00:41:39, Serial0/0/0.2 O IA 10.1.3.0/24 [110/658] via 10.10.23.2, 00:41:39, Serial0/0/0.2
a. A Type 3 LSA for 10.2.2.0/24 was filtered by both ABRs.
b. A Type 3 LSA for 10.1.2.0/24 was not filtered by both ABRs.
c. A Type 3 LSA for 10.1.3.0/24 was not filtered by at least one ABR.
d. A Type 3 LSA for 10.1.1.0/24 filtered by both ABRs.
Q2. The following command output was gathered from Router R1, an ABR between areas 0 (backbone) and area 1. In this internetwork, area 0 contains all the subnets of class A network 10.0.0.0. R1’s OSPF process has a distribute-list prefix question in command configured. Assuming the subnets listed in the answers actually exist in area 0, which of the following occurs on router R1?
R1#sh ip prefix-list ip prefix-list question: 4 entries seq 5 deny 10.1.2.0/24 ge 25 le 27 seq 15 deny 10.2.0.0/16 ge 30 le 30 seq 20 permit 0.0.0.0/0 le 32
a. R1 will not create/flood a type 3 LSA for subnet 10.1.2.0/26 into area 1.
b. R1 will not create/flood a Type 3 LSA for subnet 10.1.2.0/24 into area 1.
c. R1 will not have an OSPF route for subnet 10.1.2.0/26 in its IP routing table.
d. R1 will not have an OSPF route for subnet 10.1.2.0/24 in its IP routing table.
Q3. Use the same scenario as the previous question, with one change. Instead of the distribute-list prefix question in command configured on R1, R1’s OSPF process has an area 1 filter-list prefix question in command configured. Again assuming that the subnets listed in the answers actually exist in area 0, which of the following occurs on router R1?
R1#sh ip prefix-list ip prefix-list question: 4 entries seq 5 deny 10.1.2.0/24 ge 25 le 27 seq 15 deny 10.2.0.0/16 ge 30 le 30 seq 20 permit 0.0.0.0/0 le 32
a. R1 will not create/flood a type 3 LSA for subnet 10.1.2.0/26 into area 1.
b. R1 will not create/flood a Type 3 LSA for subnet 10.1.2.0/24 into area 1.
c. R1 will not have an OSPF route for subnet 10.1.2.0/26 in its IP routing table.
d. R1 will not have an OSPF route for subnet 10.1.2.0/24 in its IP routing table.
Q4. R1, an ABR between backbone area 0 and area 1, has intra-area routes in area 0 for 10.1.1.0/24, 10.1.2.0/24, and 10.1.3.0/24. These routes have metrics of 21, 22, and 23, respectively. An engineer then adds the area 0 range 10.1.0.0 255.255.0.0 command under the OSPF process of R1. Which of the following is true? (Choose two.)
a. R1 loses and then re-establishes neighborships with all neighbors.
b. R1 no longer advertises 10.1.1.0/24 to neighbors into area 1.
c. R1 advertises a 10.1.0.0/16 route into area 1 with a metric of 23 (largest metric).
d. R1 advertises a 10.1.0.0/16 route into area 1 with metric of 21 (lowest metric).
Q5. The following output exists on Router R1, a router internal to area 1. What can you determine as true from the output of the show ip ospf database summary command?
Routing Bit Set on this LSA LS age: 124 Options: (No TOS-capability, DC, Upward) LS Type: Summary Links (Network) Link State ID: 10.1.0.0 (summary Network Number) Advertising Router: 1.1.1.1 LS Seq Number: 80000001 Checksum: 0x878F Length: 28 Network Mask: /22 TOS: 0 Metric: 11
a. The LSA was created by an ABR due to an area range command.
b. The LSA was created by an ASBR due to a summary-address command.
c. If created by an area range command, the best metric for a subordinate subnet on that ABR must have been 11.
d. None of the other answers is correct.
Q6. Router R1, an ASBR connected to the Internet and to backbone area 0, has been configured with a default-information originate command. Which of the following is true about the effects of this configuration command?
a. R1 will always create and flood a default route into the OSPF domain.
b. R1 will create and flood an LSA for prefix/length 0.0.0.0/0 into the OSPF domain if R1’s IP routing table has a route to 0.0.0.0/0.
c. R1 will set a flag on the LSA for the subnet between itself and one of the ISPs, noting this subnet as a default network, regardless of whether R1 has a default route.
d. R1 will set a flag on the LSA for the subnet between itself and one of the ISPs, noting this subnet as a default network, but only if R1 has a route to 0.0.0.0/0.
Q7. Which of the following is true about routers internal to a totally NSSA area? (Choose two.)
a. Routers cannot redistribute external routes into the area.
b. Routers should have zero Type 3 LSAs in their LSDBs.
c. Routers should have zero Type 5 LSAs in their LSDBs.
d. Routers should learn default routes from the ABRs attached to the area.
Q8. ABR R1 has been configured with an area 1 stub no-summary command. Which stubby area type is area 1?
a. Stub
b. Totally stubby
c. NSSA
d. Totally NSSA