CCNP Route FAQ: OSPF Topology, Routes, and Convergence
Q1. 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?
e. None of the other answers is correct.
Q2. 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 BDR.
e. None of the other answers is correct.
Q3. 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.
Q4. Which of the following OSPF messages contains entire complete LSAs used during the database exchange process?
Q5. 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 18.104.22.168 all-DR-routers multicast address.
b. R5 will send its DD, LSR, and LSU packets to the 22.214.171.124 all-DR-routers multicast address.
c. The DR will inform R5 about LSAs by sending its DD, LSR, and LSU packets to the 126.96.36.199 all-SPF-routers multicast address.
d. The DR will inform R5 about LSAs by sending its DD, LSR, and LSU packets to the 188.8.131.52 all-SPF-routers multicast address.
Q6. R1 is internal to area 1, and R2 is internal to area 2. Subnet 10.1.1.0/24 exists in area 2 as a connected subnet off R2. ABR ABR1 connects area 1 to backbone area 0, and ABR2 connects area 0 to area 2. Which of the following LSAs must R1 use when calculating R1’s best route for 10.1.1.0/24?
a. R2’s Type 1 LSA
b. Subnet 10.1.1.0/24’s Type 2 LSA
c. ABR1’s Type 1 LSA in area 0
d. Subnet 10.1.1.0/24’s Type 3 LSA in Area 0
e. Subnet 10.1.1.0/24’s Type 3 LSA in Area 1
Figure: Comparing a Single Area LSDB to a Three Area LSDB
Q7. Which of the following LSA types describes topology information that, when changed, requires a router in the same area to perform an SPF calculation? (Choose two.)
Q8. The following output was taken from Router R3. A scan of R3’s configuration shows that no bandwidth commands have been configured in this router. Which of the following answers lists configuration settings could be a part of a configuration that results in the following output? (Choose two.)
R3#show ip ospf interface brief
Interface PID Area IP Address/Mask Cost State Nbrs F/C
Se0/0/0.2 3 34 10.10.23.3/29 647 P2P 1/1
Se0/0/0.1 3 34 10.10.13.3/29 1000 P2P 1/1
Fa0/0 3 34 10.10.34.3/24 20 BDR 1/1
a. An auto-cost reference-bandwidth 1000 command in router ospf mode
b. An auto-cost reference-bandwidth 2000 command in router ospf mode
c. An ip ospf cost 1000 interface S0/0/0.1 command in router ospf mode
d. An auto-cost reference-bandwidth 64700 command in router ospf mode
Q9. Which of the following LSA types describe information related to topology or subnets useful for calculating routes for subnets inside the OSPF domain? (Choose three.)