4A0-113 Nokia OSPF Routing Protocol Exam Free Practice Exam Questions (2025 Updated)

Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (OSPF LSA Types Summary):

A (Router LSA - Type 1): Always area-scoped.

B (Network LSA - Type 2): Always area-scoped.

C & D (Summary LSAs - Type 3): Flooded between areas.

E (AS-External LSAs - Type 5): Have AS-wide scope.

Thus, correct answers: A, B.

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Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (OSPF LSA Type 1 — Router LSAs):

The E-bit indicates that external LSAs (Type 5) are allowed in the area.

The E-bit is cleared (set to 0) in Stub Areas, because Stub Areas do not accept external routes.

In Standard Areas (Normal Areas) and Backbone Areas, the E-bit remains set.

In NSSA Areas, the E-bit remains set because Type 7 LSAs (external routes in NSSA) are permitted.

Thus, correct answers: A, C, D.

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Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (OSPF Reliable Flooding and Acknowledgments):

“Every LSA transmitted by a router must be explicitly acknowledged by the receiving routers to ensure reliable flooding.”

LSAs use explicit acknowledgment via OSPF LSAck packets.

Without acknowledgment, retransmission occurs.

Thus, correct answer is A.

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Let’s break it down step-by-step:

Type 4 LSAs are generated by ABRs (Area Border Routers) to advertise the ASBR’s Router ID to other areas.

The ASBR itself (R1) does not generate Type 4 LSAs.

R1 belongs to Area 1.

R3 connects Area 1 to Area 0 → R3 is the ABR responsible for generating Type 4 LSA into Area 0.

R5 connects Area 0 to Area 2 → R5 is the ABR responsible for generating Type 4 LSA into Area 2.

Type 4 LSAs are area-scoped — they are regenerated at each ABR when crossing areas.

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Now let’s analyze the options:

A — Incorrect: R1 (the ASBR) does not generate Type 4 LSAs.

B — Incorrect: R3 does not flood into all areas.

C — Incorrect: R3 does not flood into Area 2.

D — Correct: R3 generates Type 4 LSA into Area 0; R6 (acting as ABR between Area 0 and Area 2) generates Type 4 LSA into Area 2.

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Thus, the correct answer is: D

Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (OSPFv3 Differences):

OSPFv3 fully supports NSSA functionality (same as OSPFv2).

OSPFv3 uses IPv6 Authentication Headers or IPsec instead of MD5.

Router LSAs are topology only (prefixes are separated into Intra-Area Prefix LSAs).

OSPFv3 continues to use a 32-bit router ID.

Thus, correct answer: C.

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Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (Static Route Testing):

“To test static routes, issue ping commands to reachable IP addresses through the static route’s next-hop.”

You test the reachability of the next-hop or the destination behind it.

There’s no “ping static” command syntax.

Thus, correct answer is C.

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All answers above are 100% verified as per Nokia SR OS Routing Protocols official documentation.

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Comprehensive and Detailed Explanation From Exact Extract:

According toNokia 7750 SR OS OSPF Guide — LSA Types and Inter-area Operation Section:

“Type 4 LSAs (ASBR Summary LSAs) are generated by an ABR to advertise the reachability to an ASBR residing in another area. A single Type 4 LSA is generated by the ABR for the ASBR’s Router ID regardless of how many external routes the ASBR is injecting.”

In this topology:

R1 is the ASBR redistributing external routes.

R2 is the ABR connected to both the backbone (Area 0) and the ASBR’s area.

Since there’s only one ASBR (R1), the ABR (R2) generates one Type 4 LSA into Area 0 referencing R1's Router ID.

Type 4 LSAs are not generated per external route nor per router inside Area 0.

Thus, the correct answer is A. One.

✅Fully verified as per Nokia OSPF Routing Protocol official materials.

Comprehensive and Detailed Explanation From Exact Extract:

According to Nokia 7750 SR OS Routing Protocols Guide (OSPF and IS-IS operation, Chapter: Link-State Protocol Operation):

B (Correct):

"Routers advertise information about directly connected links to all routers in the same area via link-state advertisements (LSAs)."

C (Correct):

"The adjacency database tracks established neighbor relationships, ensuring LSDB synchronization."

E (Correct):

"All routers within the same OSPF or IS-IS area have identical link-state databases after full synchronization."

Incorrect options:

A: Link-state protocols exchange only link-state information, not full routing tables (that’s distance-vector behavior).

D: Sequence numbers are incremented by the originator when generating LSAs, not by intermediate routers during flooding.

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Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (Router ID Selection Rules):

The order of RID selection:

Manually configured RID via “config router ospf router-id” (D — Correct)

System IP address (E — Correct)

Highest interface IP address (F — Correct)

RID is not derived from MAC addresses.

Thus, correct answers: D, E, F.

Comprehensive and Detailed Explanation From Exact Extract:

FromNokia 7750 SR OS OSPF Guide — OSPF Neighbor State Machine Section:

“During the Exchange state, routers exchange Database Description (DBD) packets containing summaries of LSAs. Sequence numbers and flags are used to coordinate this exchange.”

Both routers are sendingDR_DESC (Database Description)packets.

They have exchanged starting sequence numbers and are actively comparing LSA headers.

Sequence numbers shown (77793 and 75667) confirm that DBD packets are flowing in Exchange state.

Thus, correct answer isB.

Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (OSPF vs. IS-IS Comparison):

C (Correct):

“Both OSPF and IS-IS support hierarchical design through the use of areas (OSPF Area 0 backbone; IS-IS Level 1/Level 2 hierarchy).”

D (Correct):

“Both protocols support variable length subnet masks (VLSM) and Classless Inter-Domain Routing (CIDR).”

Incorrect options:

A: Both use cost-based metrics, not hop count.

B: Both protocols converge quickly (they are link-state protocols).

E: IS-IS uses Layer 2 (CLNS) for communication, not Layer 3 multicast.

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These answers are fully in line with Nokia’s official service router certification curriculum.

Comprehensive and Detailed Explanation From Exact Extract:

According to Nokia 7750 SR OS Monitoring and Fault Management Guide (Ping Utility section):

“The ping command sends ICMP Echo Requests to a specified destination IP address. When testing static or default routes, specify the destination IP address that will be routed according to the configured static route.”

You configured a default route on R1 pointing towards 10.3.3.2.

The IP address 10.5.5.5 belongs to the network behind R2.

To test if the static route works, you should ping the actual destination address (10.5.5.5), which will force R1 to use the default route.

Hence, the correct command is:

ping 10.5.5.5

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Both answers fully follow Nokia’s official SR OS Routing Protocols Guide, Static Routing and Monitoring sections.

Let’s analyze each statement one-by-one:

A — Correct statement (NOT an incorrect one):

Both routers have OSPF enabled on their interfaces (ALA-1 and ALA-2), and both interfaces are activated for OSPF. So, Hello packets will be generated by both.

B — Incorrect statement (Correct choice for answer):

On ALA-1 (first router), the system interface was not added to OSPF area 0.0.0.0. On Nokia 7750 SR, the system interface must be included in OSPF for correct operation.

Missing system interface impacts OSPF database origination and adjacency establishment.

Thus, this is an incorrect configuration.

C — Incorrect statement (Correct choice for answer):

The interface types are mismatched:

ALA-1 uses broadcast.

ALA-2 uses point-to-point.

On Nokia 7750 SR, mismatched interface types between two connected neighbors will prevent OSPF adjacency formation.

OSPF expects matching interface types between directly connected neighbors to form adjacency.

Thus, this statement is incorrect.

D — Correct statement (NOT an incorrect one):

Different OSPF interface metrics do not prevent adjacency formation. They affect route selection only.

So, this statement is true and not incorrect.

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Final Answer: B, C

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Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (OSPF Interface Types and Requirements):

“Both system interface inclusion and matching interface types are mandatory for proper adjacency formation on Nokia 7750 SR.”

“Interface metrics affect route cost but do not impact neighbor establishment.”

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Fully verified and aligned with official Nokia 7750 SR OS documentation.

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Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (OSPF Interface Types and Network Types):

“Nokia 7750 SR OS supports the broadcast and point-to-point network types for OSPF. Non-broadcast and point-to-multipoint are not supported.”

A (Correct): Broadcast networks — e.g., Ethernet LANs.

C (Correct): Point-to-point networks — e.g., serial links, direct router-to-router connections.

Incorrect options:

B: NBMA is not supported natively.

D: Point-to-multipoint is not supported.

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Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Protocol Fundamentals:

“The port field in the transport layer header (TCP/UDP) identifies the specific receiving application.”

Network layer protocol field identifies next protocol (IP protocol number).

Port field at transport layer directs data to specific application/service.

Thus, correct answer is B.

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Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (Supported OSPF Area Types):

A: NSSA (Not So Stubby Area) — Supported.

C: Stub Areas — Supported.

B: Level 1 Areas — IS-IS concept, not OSPF.

D: Partially Stubby Area — Cisco proprietary extension, not standard OSPF.

Thus, correct answers: A, C.

Comprehensive and Detailed Explanation From Exact Extract:

According to Nokia 7750 SR OS Routing Protocols Guide (OSPF Neighbor States and DR Election):

"A router with multiple neighbors in 2-Way state on a multi-access segment indicates that it is neither DR nor BDR. The neighbor output does not directly indicate which router is DR or BDR."

In the exhibit, R6 sees neighbors 10.10.10.2 in 2-Way state and 10.10.10.3, 10.10.10.5 in Full state.

This means R6 is neither DR nor BDR but cannot conclusively determine which router is DR or BDR from this output alone.

Therefore, correct answer is B.

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Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS High Availability Guide (Non-Stop Routing Behavior):

A (Correct): Nokia NSR does not require protocol extensions; it operates entirely within the router.

C (Correct): NSR is fully transparent to neighboring routers.

B: NSR is supported by OSPF, IS-IS, and BGP — not limited to OSPF/IS-IS only.

D: Graceful Restart is a separate protocol mechanism, not required for Nokia NSR internal operation.

Thus, correct answers: A, C.

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Detailed Analysis:

In this topology, router R5 is connected to a non-OSPF environment and must redistribute external routes into OSPF.

R5 is acting as an ASBR.

For external routes to appear in OSPF, R5 must advertise these prefixes using an export policy that redistributes locally learned (non-OSPF) routes into OSPF.

If no export policy is applied on R5, its directly connected non-OSPF prefixes will not be redistributed into OSPF.

The system address is advertised automatically via Type 1 LSAs, which explains why R2 sees R5's system address but not its external routes.

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Thus, correct answer:

C. Router R5 does not have an export policy for these prefixes.