3.4 Configure and verify single area OSPFv2.
Objective 3.4 sits in IP Connectivity, which carries 25% of the CCNA exam. The questions below are original, written from the official objective title above, and each explanation cites the Cisco page it rests on.
Objective title verbatim from the official objectives. Cisco exam page ↗
A worked example
Shown solved, with the whole explanation open: this is what every question here carries.
An engineer starts an OSPF process on this router and enters no router-id command.
Device# show ip interface brief
Interface IP-Address OK? Method Status Protocol
GigabitEthernet1/0/1 10.1.1.1 YES manual up up
GigabitEthernet1/0/2 172.16.5.1 YES manual up up
Loopback0 192.168.10.1 YES manual up up
Loopback1 192.168.9.1 YES manual up upWhich address becomes the router ID?
The concept
A router ID has to stay fixed, as losing it forces the process to recalculate and reflood everything it knows. The selection therefore favours the one kind of interface that cannot go down, and only falls back to physical addressing when none exists.
Why this answer
Two loopbacks are present, so the physical interfaces are out of the running whatever their addressing. Between the two loopbacks the higher numeric address is taken, and 192.168.10.1 is higher than 192.168.9.1.
- AA physical interface is considered only when the router has no loopback configured.
- BThis is the lowest address on the device, and low addressing is never what the selection reaches for.
- Correct. It is the higher of the two loopback addresses.
- DThis loopback is eligible but loses on numeric value in the third octet, 9 against 10.
Now you: objective 3.4 questions
No account needed. The explanation opens when you answer.
Sample question 1 of 3
A candidate notices that three OSPF entries learned in three different ways all carry the same first bracket value.
O 10.20.0.0/16 [110/12] via 10.0.0.2, 00:41:02, GigabitEthernet1/0/1
O IA 10.30.0.0/16 [110/74] via 10.0.0.2, 00:40:58, GigabitEthernet1/0/1
O E2 10.40.0.0/16 [110/20] via 10.0.0.2, 00:12:11, GigabitEthernet1/0/1What is that 110?
Sample question 2 of 3
R1 and R2 sit on one link and never reach full adjacency.
R1 configuration
router ospf 1
network 10.0.0.0 0.0.0.3 area 0
interface GigabitEthernet1/0/1
ip address 10.0.0.1 255.255.255.252
ip ospf hello-interval 5
R2 configuration
router ospf 2
network 10.0.0.0 0.0.0.3 area 0
interface GigabitEthernet1/0/1
ip address 10.0.0.2 255.255.255.252
ip ospf hello-interval 10Which difference explains it?
Sample question 3 of 3
An engineer adds network 10.1.1.0 0.0.0.255 area 0 under an OSPF process. What does that statement settle?
That’s 3 of the full CCNA bank.
Keep going free: 10 questions per certification in bank practice, with no account.
Continue practicingRead the sources
These are the official pages the questions above cite. Reading them is studying the objective from the primary source, which is what the explanations point you toward anyway.