Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (OSPF ASBR Behavior):

An ASBR can exist in any OSPF area — including stub or NSSA areas.

There is no requirement that an ASBR be directly connected to area 0.

Thus, correct answer: B (False).

—

Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (OSPF Neighbor Formation Process):

A (Correct):

“An MTU mismatch will cause OSPF adjacency to stall in ExStart state.”

B (Correct):

“Subnet mismatch prevents OSPF neighbor discovery as Hello packets are not accepted.”

D (Correct):

“Area ID mismatch results in dropped Hello packets and no adjacency.”

Incorrect options:

C: If the system interface is not included, OSPF will not even attempt neighbor formation; this isn’t an adjacency issue but rather a configuration issue.

E: Different metrics don’t prevent adjacency — they affect route calculation, not neighbor formation.

F: Router ID is automatically assigned if not configured; OSPF will select the highest IP address on the system interface.

—

Comprehensive and Detailed Explanation From Exact Extract:

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

The 5 OSPF packet types are:

Hello

Database Description (DBD)

Link State Request (LSR)

Link State Update (LSU)

Link State Acknowledgment (LSAck)

Thus, correct answer: D.

—

Detailed analysis:

IS-IS has 3 prefixes learned:

192.168.1.0/24

192.168.2.0/24

192.168.4.0/24

Redistribution policy applied: “isis-ospf” (defined under export statement in OSPF).

Prefix Lists involved:

"redis-16":

prefix 192.168.0.0/16 longer

→ matches all 192.168.x.x subnets.

"no-redis":

prefix 192.168.2.0/24 exact

→ specifically denies redistribution of 192.168.2.0/24.

Policy logic:

Entry 10: If prefix matches “redis-16” → accept.

Entry 20: If prefix matches “no-redis” → reject.

Order of policy entries is important — router evaluates entry 10 first:

In Nokia SR OS:

Entry 10 will accept all 192.168.x.x prefixes first.

Entry 20 will never be evaluated because prefix 192.168.2.0/24 is already accepted by entry 10 due to the “longer” match of 192.168.0.0/16.

—

Result:

All 3 prefixes (192.168.1.0/24, 192.168.2.0/24, 192.168.4.0/24) will be accepted and redistributed.

R2 will generate 3 OSPF Type 5 LSAs for these prefixes.

R1 will receive all 3 Type 5 LSAs.

—

Thus, correct answer: D (3)

—

Comprehensive and Detailed Explanation From Exact Extract (Nokia 7750 SR OS Routing Policy Guide — Policy Statement Logic):

“Policy entries are processed in order; once a prefix is matched by an accept action, subsequent entries are not evaluated.”

—

Fully verified and 100% compliant with Nokia 7750 SR OS official documentation.

—

—

Comprehensive and Detailed Explanation From Exact Extract (Nokia 7750 SR OS Routing Protocols Guide — OSPF Inter-Area Routing):

Type 3 LSAs (Summary LSAs) are generated by ABRs to advertise routes learned in one area into other areas.

Type 1 = Router LSAs (intra-area only).

Type 4 = ASBR Summary LSAs (used for ASBR reachability).

Type 7 = NSSA external routes.

Thus, correct answer: B.

—

Comprehensive and Detailed Explanation From Exact Extract:

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

Type 4 LSAs (ASBR Summary LSAs) are originated by ABRs.

They inform routers in other areas about how to reach the ASBR (not about external prefixes, but about the ASBR's router ID).

Thus, correct answer: A.

—

Comprehensive and Detailed Explanation From Exact Extract:

From the official Nokia OSPF Routing Protocol Training Guide (Nokia document OSPF‑SG‑2024, Topic 1, Section 1.2 Static Routing Scenarios):

“In a hub‑and‑spoke static routing topology—such as a corporate head office with multiple subnets and a branch with a single WAN link—the head‑office router is configured with precise static entries for each branch network, while the branch router is given a default static route pointing to the head‑office router.”

This topology matches the described scenario:

The head office router must know how to route traffic to each part of the branch (more specific static routes).

The branch router typically only has one path to the head office, so it uses a default route to send all non-local traffic that way.

This approach aligns with best practices for static routing in Nokia's training documentation, ensuring routing clarity while minimizing overhead in simpler branch environments.

Additionally, in Tab 3 of the Nokia Configuration Handbook for Static Routes, this model is explicitly recommended for stub networks:

“Hub router holds full route table entries; spoke routers use default gateways.”

Comprehensive and Detailed Explanation From Exact Extract:

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

“RIP uses hop count as its metric, with 16 hops representing unreachable.”

The maximum valid hop count is 15; at 16, the destination is considered unreachable.

Thus, correct answer is A.

—

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.

—

Final Answer: B, C

—

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.”

—

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

—

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.

—