300-410 OSPF Troubleshooting (v2/v3) Practice Test 2 — 15 Questions

Question 1

A network engineer runs the following command on Router R1:

R1# show ip ospf virtual-links

Virtual Link OSPF_VL0 to router 10.1.1.3 is up
  Run as demand circuit
  DoNotAge LSA allowed.
  Transit area 1, via interface GigabitEthernet0/0, Cost of using 10
  Transmit Delay is 1 sec, State POINT_TO_POINT,
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    Hello due in 00:00:08
  Adjacency State FULL

Based on this output, what can be concluded?

Accepted Answer

The virtual link is functioning correctly and the adjacency is full.. The virtual link to router 10.1.1.3 is up and in FULL state. It is running as a demand circuit, which suppresses hello packets when the link is stable. The transit area is area 1.

Answer

The virtual link is using area 0 as the transit area.

Answer

Router R1 is not receiving hello packets on the virtual link.

Answer

The virtual link has a cost of 1.

Question 2

A network engineer runs the following command on Router R1:

R1# show ip ospf neighbor detail

Neighbor 10.1.1.4, interface address 192.168.14.4
    In the area 0 via interface GigabitEthernet0/2
    Neighbor priority is 1, State is 2WAY, 2 state changes
    DR is 10.1.1.1, BDR is 10.1.1.4
    Options is 0x12 (L L S R)
    Dead timer due in 00:00:38
    Neighbor is up for 00:05:22
    Index 1/1/1, retransmission queue length 0, number of retransmission 0
    First 0x0(0)/0x0(0) Next 0x0(0)/0x0(0)
    Last retransmission scan length is 0, time is 0 msec
    Last retransmission scan time is 0 msec

Based on this output, what is the problem?

Accepted Answer

The neighbor is in 2WAY state, meaning the adjacency is not fully established.. The neighbor state is 2WAY, not FULL. This indicates that the neighbor relationship has not progressed to full adjacency. On a broadcast network, routers in 2WAY state have exchanged hello packets but have not completed database exchange. This could be due to mismatched MTU, authentication, or other issues, but the key observation is that the state is not FULL.

Answer

Router R1 is the DR and the neighbor is the BDR, so the state is correct.

Answer

The dead timer is about to expire, causing the neighbor to go down.

Answer

The neighbor has a lower priority than R1, so it remains in 2WAY.

Question 3

A network engineer runs the following command on Router R1:

R1# show ipv6 ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
10.1.1.2         1   FULL/BDR        00:00:35    FE80::2          GigabitEthernet0/0
10.1.1.3         1   FULL/DR         00:00:32    FE80::3          GigabitEthernet0/1

Based on this output, which statement is correct regarding OSPFv3?

Accepted Answer

Router R1 has a full adjacency with both neighbors in OSPFv3.. The output shows OSPFv3 neighbors. The neighbor 10.1.1.2 is in state FULL/BDR, meaning it is the Backup Designated Router. The neighbor 10.1.1.3 is in state FULL/DR, meaning it is the Designated Router. The addresses are link-local IPv6 addresses.

Answer

Router R1 is the DR on the segment connected to GigabitEthernet0/0.

Answer

The OSPFv3 process is using IPv4 addresses as router IDs.

Answer

Router R1 is not receiving hello packets from 10.1.1.3.

Question 4

Examine the following OSPF configuration on router R1:

router ospf 1
 network 10.0.0.0 0.255.255.255 area 0
 network 192.168.1.0 0.0.0.255 area 1

What is the effect of this configuration?

Accepted Answer

All interfaces with IP addresses in the 10.0.0.0/8 range will be enabled for OSPF in area 0, and interfaces in 192.168.1.0/24 will be in area 1.. The network statements define which interfaces participate in OSPF and assign them to areas. The first statement covers all interfaces with IP addresses starting with 10.x.x.x, and the second covers 192.168.1.x. This is a valid configuration.

Answer

Only the interface with IP 10.0.0.1 will be in area 0; all other 10.x.x.x interfaces are ignored.

Answer

The configuration is invalid because OSPF process 1 cannot have two network statements in different areas.

Answer

The configuration will cause a routing loop between area 0 and area 1.

Question 5

Consider this OSPFv3 configuration on router R2:

ipv6 router ospf 10
 router-id 2.2.2.2
 area 0 authentication ipsec spi 256 md5 1234567890abcdef1234567890abcdef

interface GigabitEthernet0/0
 ipv6 address 2001:db8:1::1/64
 ipv6 ospf 10 area 0

What is the effect of this configuration?

Accepted Answer

OSPFv3 will use IPsec MD5 authentication for all packets in area 0, including on GigabitEthernet0/0.. The area authentication command under OSPFv3 enables IPsec authentication for the entire area. The interface is enabled for OSPFv3 in area 0, so it will use the area authentication. However, OSPFv3 authentication uses IPsec AH or ESP; the configuration shown is valid.

Answer

Authentication is applied only to the GigabitEthernet0/0 interface, not the entire area.

Answer

The configuration is invalid because OSPFv3 does not support IPsec authentication.

Answer

The router-id is missing, so OSPFv3 will not start.

Question 6

Examine this OSPF configuration snippet on router R3:

router ospf 1
 network 10.1.1.0 0.0.0.255 area 0
 default-information originate always

What is the effect of the default-information originate always command?

Accepted Answer

R3 will unconditionally advertise a default route into OSPF as an external LSA type 5.. The command injects a default route (0.0.0.0/0) into the OSPF domain as an external LSA type 5, regardless of whether the router has a default route in its routing table. The 'always' keyword forces advertisement even without a default route.

Answer

R3 will advertise a default route into OSPF only if it has a default route in its routing table.

Answer

R3 will advertise a default route only if it is an ASBR.

Answer

The command is invalid because default-information originate requires a route-map.

Question 7

Consider this OSPF configuration on router R4:

router ospf 1
 network 192.168.1.0 0.0.0.255 area 0
 neighbor 10.0.0.2

What is the effect of the neighbor statement?

Accepted Answer

The neighbor command is ignored because the network type is broadcast by default on Ethernet interfaces.. The neighbor command is used in OSPF for non-broadcast multi-access (NBMA) networks to manually specify neighbors. However, the interface used to reach 10.0.0.2 must be configured with the appropriate network type (e.g., point-to-multipoint or non-broadcast). If the network type is broadcast or point-to-point, the neighbor command is ignored.

Answer

R4 will attempt to form an OSPF adjacency with 10.0.0.2 over any interface that can reach it.

Answer

R4 will send unicast OSPF packets to 10.0.0.2, but only if the interface is in area 0.

Answer

The configuration is invalid because the neighbor command must include a priority.

Question 8

Examine this OSPF configuration on router R5:

router ospf 1
 network 10.0.0.0 0.255.255.255 area 0
 passive-interface default
 no passive-interface GigabitEthernet0/0

What is the effect of the passive-interface default command?

Accepted Answer

All interfaces except GigabitEthernet0/0 will be passive; GigabitEthernet0/0 will send and receive OSPF hellos.. The passive-interface default command sets all interfaces as passive by default, meaning they will not send OSPF hello packets or form adjacencies. The no passive-interface command then overrides this for the specified interface, allowing it to form adjacencies.

Answer

All interfaces are passive, including GigabitEthernet0/0, because the no passive-interface command is ignored.

Answer

Only interfaces with network statements will be affected; other interfaces remain active.

Answer

The configuration is invalid because passive-interface default cannot be used with OSPF.

Question 9

Consider this OSPF configuration on router R6:

router ospf 1
 network 10.0.0.0 0.255.255.255 area 0
 area 0 stub

What is the effect of the area 0 stub command?

Accepted Answer

The configuration is rejected by IOS because the backbone area cannot be a stub.. The area 0 stub command is invalid because area 0 (the backbone) cannot be configured as a stub area. Stub areas are used to reduce LSA flooding, but the backbone must have full routing information. This configuration will be rejected by IOS.

Answer

Area 0 will become a stub area, blocking type 5 LSAs from entering the backbone.

Answer

The command is ignored, and area 0 remains a normal area.

Answer

Only type 5 LSAs are blocked, but type 3 and 4 LSAs are still allowed.

Question 10

What is the default OSPF hello interval on a point-to-point serial interface?

Accepted Answer

10 seconds. OSPF hello interval defaults are based on the network type. For point-to-point and broadcast networks, the default hello interval is 10 seconds. For NBMA and point-to-multipoint, it is 30 seconds.

Answer

30 seconds

Answer

40 seconds

Answer

20 seconds

Question 11

Which OSPF LSA type is used to advertise prefixes from other areas into the backbone area?

Accepted Answer

Type 3 (Summary LSA). Type 3 LSAs (Summary LSAs) are generated by Area Border Routers (ABRs) to advertise networks from one area to another. They are used to propagate inter-area routes.

Answer

Type 1 (Router LSA)

Answer

Type 2 (Network LSA)

Answer

Type 5 (External LSA)

Question 12

In OSPFv3, what is the purpose of the link-local address in the neighbor adjacency process?

Accepted Answer

The link-local address is used as the source address for OSPFv3 packets and for next-hop resolution.. OSPFv3 uses link-local addresses for neighbor discovery and as the source address for OSPF packets. This is a change from OSPFv2, which uses the interface's IPv4 address. The link-local address is used for next-hop resolution and adjacency formation.

Answer

The link-local address is used as the router ID for OSPFv3.

Answer

The link-local address is only used for DR/BDR election.

Answer

The link-local address is not used in OSPFv3; global unicast addresses are used instead.

Question 13

Which TWO commands would a network engineer use to verify OSPFv2 neighbor state and adjacency issues on a Cisco IOS router? (Choose TWO.)

Accepted Answer

show ip ospf neighbor. The 'show ip ospf neighbor' command displays the state of all OSPF neighbors, while 'debug ip ospf adj' provides real-time adjacency events. 'show ip route ospf' shows routes, not neighbor states; 'show ip ospf interface' shows per-interface details but not neighbor states directly; 'show ip protocols' displays routing process info, not neighbor states.

Answer

show ip route ospf

Answer

show ip ospf interface

Answer

show ip protocols

Question 14

Which TWO statements about OSPFv3 (OSPF for IPv6) are true when comparing it to OSPFv2? (Choose TWO.)

Accepted Answer

OSPFv3 uses link-local IPv6 addresses for neighbor discovery.. OSPFv3 runs on a per-link basis (not per-subnet) and uses link-local addresses for neighbor discovery. OSPFv3 still uses areas and LSAs, and authentication is handled by IPsec, not OSPF itself. OSPFv3 does not use the 'network' command; it uses 'ipv6 ospf' under the interface.

Answer

OSPFv3 uses the same LSA types as OSPFv2.

Answer

OSPFv3 supports authentication using MD5 or SHA within the OSPF packet.

Answer

OSPFv3 uses the 'network' command to enable OSPF on interfaces.

Question 15

Which THREE symptoms indicate a potential OSPFv2 neighbor adjacency problem due to a mismatch in configuration? (Choose THREE.)

Accepted Answer

The neighbor state remains stuck in INIT or EXSTART.. A mismatch in hello/dead timers, area ID, or authentication causes neighbors to stay stuck in INIT or EXSTART state. A mismatched MTU can cause stuck in EXSTART/EXCHANGE. A mismatched network type can also cause issues. Routes missing from the routing table is a symptom of many issues, not specific to mismatches.

Answer

The neighbor state is 2WAY/DROTHER.

Answer

The 'show ip ospf neighbor' output shows the neighbor but with a state of DOWN.