The Nokia OSPF Routing Protocol Exam (4A0-113)

Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (RIP Redistribution):

RIP uses hop count as a metric, while OSPF uses cost.

When redistributing OSPF routes into RIP, you must assign a valid RIP metric (hop count) through policies or default metric settings.

If no metric is assigned, redistribution will fail or install unreachable routes (default RIP maximum is 16 hops).

Thus, correct answer: A.

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 Routing Protocols Guide (Route Preference Table):

IS-IS internal route preference: 18

OSPF Type 5 external route preference: 150

“The protocol with the lower preference value wins. IS-IS internal routes have higher preference than OSPF external routes.”

Thus, the IS-IS route will be installed in the route table.

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Comprehensive and Detailed Explanation From Exact Extract:

According to Nokia 7750 SR OS OSPF Guide — OSPF Packet Transmission Section :

“OSPF is encapsulated directly over IP using protocol number 89. It does not use TCP or UDP.”

TCP (Protocol 6) → Incorrect.

UDP (Protocol 17) → Incorrect.

OSPF operates directly at IP layer using protocol number 89.

Thus, the correct answer is D .

Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (OSPF Hello Protocol Rules):

“OSPF requires the following parameters to match for neighbor establishment: Area ID, Hello interval, Dead interval, and options (including Stub flag).”

A (Correct): Area ID must match.

B (Correct): Hello and Dead intervals must match.

C (Correct): Stub flag is part of the OSPF Options field and must match.

D: Checksum applies to LSA packets, not Hello packets.

Comprehensive and Detailed Explanation From Exact Extract:

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

On point-to-point links:

No DR/BDR election occurs.

Updates are sent to multicast address 224.0.0.5 (AllSPFRouters).

Thus, correct answer: A.

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 OSPF Guide — Area Border Routers (ABRs) Section :

“An ABR is a router connected to both area 0 and at least one non-backbone area, responsible for exchanging routing information between areas.”

ABRs serve as gateways between the backbone area (area 0) and non-backbone areas.

Summarization is optional on ABRs, not mandatory.

Thus, the correct answer is C.

Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (OSPF Neighbor State Machine):

The ExStart state is where routers negotiate who will be the master during database exchange, based on router IDs.

If both routers have the same Router ID, the negotiation cannot proceed, causing the adjacency to be stuck in ExStart.

Thus, correct answer: C.

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