300-410 OSPF Troubleshooting (v2/v3) Practice Test 4 — 15 Questions

Question 1

A network engineer runs the following command to troubleshoot OSPFv3 adjacency:

R1# debug ipv6 ospf adj
*Mar  1 00:15:23.456: OSPFv3-1-IPv6 ADJ   Gi0/0: Rcv pkt from 2001:DB8:1::2, src 2001:DB8:1::2, area 0
*Mar  1 00:15:23.457: OSPFv3-1-IPv6 ADJ   Gi0/0: Nbr 2.2.2.2: Our address 2001:DB8:1::1, his address 2001:DB8:1::2
*Mar  1 00:15:23.458: OSPFv3-1-IPv6 ADJ   Gi0/0: Nbr 2.2.2.2: Neighbor is not DR, state 2WAY
*Mar  1 00:15:23.459: OSPFv3-1-IPv6 ADJ   Gi0/0: Nbr 2.2.2.2: DR is 2001:DB8:1::2, BDR is 2001:DB8:1::1
*Mar  1 00:15:23.460: OSPFv3-1-IPv6 ADJ   Gi0/0: Nbr 2.2.2.2: Build the Start DBD
*Mar  1 00:15:23.462: OSPFv3-1-IPv6 ADJ   Gi0/0: Nbr 2.2.2.2: Master/Slave negotiation done
*Mar  1 00:15:23.464: OSPFv3-1-IPv6 ADJ   Gi0/0: Nbr 2.2.2.2: Exchange done, loading started
*Mar  1 00:15:23.466: OSPFv3-1-IPv6 ADJ   Gi0/0: Nbr 2.2.2.2: Loading done
*Mar  1 00:15:23.468: OSPFv3-1-IPv6 ADJ   Gi0/0: Nbr 2.2.2.2: Full

What does this output indicate?

Accepted Answer

The OSPFv3 adjacency formed successfully between routers with router IDs 1.1.1.1 and 2.2.2.2.. The debug output shows the successful OSPFv3 adjacency formation between two routers on interface Gi0/0.

Answer

The OSPFv3 adjacency failed due to area mismatch.

Answer

The adjacency is stuck in Exstart state due to interface MTU mismatch.

Answer

The router is the DR on this segment.

Question 2

A network engineer runs the following command to verify OSPFv3 database:

R1# show ipv6 ospf database router 2.2.2.2

OSPFv3 Router with ID (1.1.1.1) (Process ID 1)

Router Link States (Area 0)

LS age: 60
  LS Type: Router Links
  Link State ID: 0.0.0.0
  Advertising Router: 2.2.2.2
  LS Seq Number: 80000003
  Checksum: 0x5678
  Length: 40
  Number of Links: 1

Link connected to: a Transit Network
     (Link ID) Interface ID: 2
     (Link Data) Neighbor Interface ID: 1
      Number of TOS metrics: 0
       TOS 0 Metrics: 10

What does this output indicate?

Accepted Answer

The LSA indicates a single transit link with interface IDs, typical for OSPFv3.. The output shows an OSPFv3 Router LSA from router 2.2.2.2 with one link to a transit network, using interface IDs instead of IP addresses.

Answer

The LSA shows a link to a stub network with prefix information.

Answer

The advertising router is 1.1.1.1.

Answer

This is a Type 5 External LSA.

Question 3

A network engineer runs the following command to troubleshoot OSPF neighbor states:

R1# show ip ospf neighbor detail
 Neighbor 2.2.2.2, interface address 10.1.1.2
    In the area 0 via interface GigabitEthernet0/0
    Neighbor priority is 1, State is FULL, 6 state changes
    DR is 10.1.1.2, BDR is 10.1.1.1
    Options is 0x42 (LLS, DC)
    LLS Options is 0x1 (LR)
    Dead timer due in 00:00:36
    Neighbor is up for 00:12:34
    Index 1/1/1
    Retransmission queue length 0, number of retransmission 1
    First 0x0(0)/0x0(0)/0x0(0) Next 0x0(0)/0x0(0)/0x0(0)
    Last retransmission scan length is 1, maximum is 1
    Last retransmission scan time is 0 msec, maximum is 0 msec

What does this output indicate?

Accepted Answer

The neighbor is the DR and the adjacency is fully established.. The output shows detailed OSPF neighbor information, including state, DR/BDR roles, and timers.

Answer

The neighbor is in the 2WAY state and not fully adjacent.

Answer

There is a retransmission queue issue causing packet loss.

Answer

The neighbor is not participating in DR/BDR election.

Question 4

A network engineer runs the following command to verify OSPF SPF calculations:

R1# show ip ospf statistics

OSPF Router with ID (1.1.1.1) (Process ID 1)

Area 0: SPF algorithm executed 12 times

SPF calculation time (in msec):
    Total: 12, Average: 1.0
    Minimum: 0, Maximum: 2
  Last SPF due to: LSA change
  Number of LSA changes: 5
  Number of LSA deletions: 2
  Number of LSA additions: 3
  Number of LSA updates: 0

Area 1: SPF algorithm executed 3 times

SPF calculation time (in msec):
    Total: 3, Average: 1.0
    Minimum: 0, Maximum: 1
  Last SPF due to: LSA change
  Number of LSA changes: 2
  Number of LSA deletions: 0
  Number of LSA additions: 2
  Number of LSA updates: 0

What does this output indicate?

Accepted Answer

Area 0 has experienced more network changes than Area 1, as indicated by higher SPF runs and LSA changes.. The output shows OSPF SPF statistics for multiple areas, including number of SPF runs and LSA changes.

Answer

The router has not performed any SPF calculations.

Answer

The SPF calculation time is too high, indicating a performance issue.

Answer

The last SPF was triggered by a timer expiry.

Question 5

A network engineer runs the following command to troubleshoot OSPF route installation:

R1# show ip route ospf
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       a - application route
       + - replicated route, % - next hop override

Gateway of last resort is not set

O    10.1.1.0/24 [110/10] via 10.1.1.2, 00:12:34, GigabitEthernet0/0
O IA 192.168.1.0/24 [110/20] via 10.1.1.2, 00:10:00, GigabitEthernet0/0
O E2 5.5.5.5/32 [110/20] via 10.1.1.2, 00:05:00, GigabitEthernet0/0

What does this output indicate?

Accepted Answer

All OSPF routes are learned from the same next-hop 10.1.1.2.. The output shows OSPF routes in the routing table, including intra-area, inter-area, and external routes.

Answer

The route to 5.5.5.5/32 is an intra-area route.

Answer

The route to 192.168.1.0/24 is a directly connected network.

Answer

The router has a default route installed.

Question 6

What is the default OSPF hello interval on a Cisco IOS-XE router for a broadcast network type?

Accepted Answer

10 seconds. The default hello interval for OSPF on broadcast and point-to-point networks is 10 seconds, as defined by RFC 2328 and implemented in Cisco IOS-XE.

Answer

30 seconds

Answer

40 seconds

Answer

60 seconds

Question 7

Which OSPF packet type is used to send link-state advertisements (LSAs) and is acknowledged by the receiver?

Accepted Answer

Link State Update (type 4). OSPF packet type 4 is the Link State Update packet, used to flood LSAs. It is acknowledged by the receiver via a Link State Acknowledgment packet (type 5).

Answer

Hello (type 1)

Answer

Database Description (type 2)

Answer

Link State Request (type 3)

Question 8

In OSPF, what is the default administrative distance for intra-area routes on a Cisco IOS-XE router?

Accepted Answer

110. Cisco IOS-XE assigns an administrative distance of 110 to all OSPF routes, including intra-area, inter-area, and external routes, unless modified.

Answer

90

Answer

115

Answer

120

Question 9

Which LSA type is used by OSPF to advertise prefixes from other routing protocols (redistribution) and has a default metric of 20?

Accepted Answer

Type 5 LSA (AS-external LSA). Type 5 AS-external LSAs are used to advertise external routes redistributed into OSPF. The default metric for these LSAs is 20, as defined by Cisco IOS.

Answer

Type 1 LSA (Router LSA)

Answer

Type 3 LSA (Summary LSA)

Answer

Type 4 LSA (ASBR Summary LSA)

Question 10

Which OSPF network type defaults to a hello interval of 30 seconds and a dead interval of 120 seconds on Cisco IOS?

Accepted Answer

Non-Broadcast (NBMA). The Non-Broadcast Multi-Access (NBMA) network type uses a default hello interval of 30 seconds and a dead interval of 120 seconds, as per Cisco implementation.

Answer

Broadcast

Answer

Point-to-point

Answer

Point-to-multipoint

Question 11

In OSPFv3, which authentication method is supported by default?

Accepted Answer

IPsec authentication. OSPFv3 uses IPsec for authentication and encryption, as defined in RFC 4552. It does not support the simple password or MD5 authentication used in OSPFv2.

Answer

MD5 authentication

Answer

Simple password authentication

Answer

No authentication is supported

Question 12

What is the default OSPF reference bandwidth used in the metric calculation on Cisco IOS-XE?

Accepted Answer

100 Mbps. Cisco IOS-XE uses a default reference bandwidth of 100 Mbps for OSPF metric calculation (cost = reference bandwidth / interface bandwidth).

Answer

1000 Mbps

Answer

10 Mbps

Answer

10000 Mbps

Question 13

Which OSPF LSA type is flooded only within the originating area and is used for loop prevention by describing the topology of the area?

Accepted Answer

Type 1 LSA (Router LSA). Type 1 Router LSAs describe the router's links and are flooded only within the area. They provide topology information for loop prevention within the area.

Answer

Type 2 LSA (Network LSA)

Answer

Type 3 LSA (Summary LSA)

Answer

Type 4 LSA (ASBR Summary LSA)

Question 14

In OSPF, what is the default behavior for auto-summary on Cisco IOS-XE?

Accepted Answer

Auto-summary is disabled by default. Cisco IOS-XE has auto-summary disabled by default for OSPF, meaning that redistributed routes are not summarized to their classful boundaries unless explicitly configured.

Answer

Auto-summary is enabled by default

Answer

Auto-summary is only enabled for external routes

Answer

Auto-summary is enabled only for inter-area routes

Question 15

Drag and drop the steps to troubleshoot OSPF DR/BDR election on a multi-access segment into the correct order, from first to last.

Accepted Answer

Verify current DR/BDR roles with show ip ospf interface. The correct order ensures that the OSPF DR/BDR election is properly influenced. First, verify the current DR/BDR roles using show ip ospf interface. Next, set the OSPF priority on the desired router to a higher value than the current DR. Then, clear the OSPF process on all routers to force a new election. After that, verify the new DR/BDR roles have been elected as expected. Finally, confirm that adjacencies are formed with the new DR/BDR.