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66.
A network design shows area 1 with three internal routers, area 0 with four internal
routers, and area 2 with five internal routers. Additionally, one ABR (ABR1) connects
areas 0 and 1, plus a different ABR (ABR2) connects areas 0 and 2. How many Type
1 LSAs would be listed in ABR2's LSDB?
- A.6
- B.7
- C.15
- D.12
- E.None of the other answers are correct
- Answer & Explanation
- Report
Answer : [D]
Explanation :
Explanation :
| As an ABR connected to areas 0 and 2, ABR2 will have LSDB entries for both area 0 and area 2. In area 0, ABR2 learns Type 1 LSAs from the four routers internal to area 0, plus ABR1, and plus 1 for the area 0 Type 1 LSA that ABR2 creates for itself. In area 2, ABR2 learns 1 each for the five routers internal to area 2, plus the 1 Type 1 LSA ABR2 created for itself inside area 2. The total is 12. |
67.
A network planning diagram shows a large internetwork with many routers. The configurations
show that OSPF has been enabled on all interfaces, IP addresses correctly
configured, and OSPF working. For which of the following cases would you expect a
router to create and flood a Type 2 LSA?
- A.When OSPF is enabled on a LAN interface, and the router is the only router connected to the subnet
- B.When OSPF is enabled on a point-to-point serial link, and that router has both the higher router ID and higher interface IP address on the link
- C.When OSPF is enabled on a Frame Relay point-to-point subinterface, has the lower RID and lower subinterface IP address, and otherwise uses default OSPF configuration on the interface
- D.When OSPF is enabled on a working LAN interface on a router, and the router has been elected as a BDR
- E.None of the other answers are correct.
- Answer & Explanation
- Report
Answer : [E]
Explanation :
Explanation :
| OSPF creates a Type 2 LSA for a subnet when the router interface connected to the subnet calls for the election of a designated router (DR) and at least two routers have discovered each other and elected a DR. Then, the DR creates and floods the Type 2 LSA. IOS by default does not elect a DR on point-to-point topologies. It does on router LAN interfaces. One answer states that one router only exists in the subnet, so it does not actually find a second router and elect a DR. In the other case, a DR and BDR have been elected, but the router described in the answer is the BDR, not the DR. So, none of the other answers is correct. |
68.
A verification plan shows a network diagram with branch office Routers B1 through
B100, plus two ABRs, ABR1 and ABR2, all in area 100. The branches connect to the
ABRs using Frame Relay point-to-point subinterfaces. The verification plan lists the
output of the show ip ospf database summary 10.100.0.0 command on a Router
B1, one of the branches. Which of the following is true regarding the output that
could be listed for this command?
- A.The output lists nothing unless 10.100.0.0 has been configured as a summary route using the area range command.
- B.If 10.100.0.0 is a subnet in area 0, the output lists one Type 3 LSA, specifically the LSA with the lower metric when comparing ABR1's and ABR2's LSA for 10.100.0.0.
- C.If 10.100.0.0 is a subnet in area 0, the output lists two Type 3 LSAs, one each created by ABR1 and ABR2
- D.None, because the Type 3 LSAs would exist only in the ABR's LSDBs.
- Answer & Explanation
- Report
Answer : [C]
Explanation :
Explanation :
| Each ABR, by definition, creates a single Type 3 LSA to represent a subnet known in one area to be advertised into another area. Assuming that 10.100.0.0 is a subnet in area 0, both ABR1 and ABR2 would advertise a Type 3 LSA into area 100. The show ip ospf database summary command specifically lists Type 3 network summary LSAs. |
69.
Which of the following OSPF messages contains complete LSAs used during the
database exchange process?
- A.LSR
- B.LSAck
- C.LSU
- D.DD
- E.Hello
- Answer & Explanation
- Report
Answer : [C]
Explanation :
Explanation :
| The Database Description (DD) packet lists a short LSA header but not the entire LSA. The Link State Request (LSR) packet asks the neighbors for a copy of an LSA. The Link State Update (LSU) holds the LSAs. LSAck simply acknowledges received LSAs, and Hello is used for neighbor discovery and neighbor state maintenance. |
70.
Routers R1, R2, R3, and R4 connect to the same 10.10.10.0/24 LAN-based subnet.
OSPF is fully working in the subnet. Later, R5, whose OSPF priority is higher than
the other four routers, joins the subnet. Which of the following are true about the
OSPF database exchange process over this subnet at this point? (Choose two.)
- A.R5 will send its DD, LSR, and LSU packets to the 224.0.0.5 all-DR-routers multicast address.
- B.R5 will send its DD, LSR, and LSU packets to the 224.0.0.6 all-DR-routers multicast address.
- C.The DR will inform R5 about LSAs by sending its DD, LSR, and LSU packets to the 224.0.0.6 all-SPF-routers multicast address.
- D.The DR will inform R5 about LSAs by sending its DD, LSR, and LSU packets to the 224.0.0.5 all-SPF-routers multicast address.
- Answer & Explanation
- Report
Answer : [B and D]
Explanation :
Explanation :
| Because the subnet was stable before R5 arrived, the other routers will have elected a DR and BDR. OSPF does not preemptively elect a new DR or BDR, so R5 will be neither (DROther). As a result, R5's messages to the DR will be sent to the 224.0.0.6 all-DR-routers multicast address, and the DR's messages directed to R5 will be sent to the 224.0.0.5 all-SPF-router address. |
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