Nokia Updated 4A0-113 Exam Questions and Answers by theia

Comprehensive and Detailed Explanation From Exact Extract:

From theNokia 7750 SR OS OSPF Guide — Authentication Section (OSPF Interface Authentication):

“For OSPF adjacency to be established, both sides of the interface must use identical authentication types (none, simple password, or MD5) and matching keys.”

Now let’s analyze the configuration provided:

Router R3:

interface "toR1"

authentication-type password

authentication-key "1vX6X/.../F4e5SKH." hash2

Router R1:

interface "toR3"

authentication-type password

message-digest-key 1 md5 d70aa...mftS hash2

On R3,authentication-type passwordmeans it is using simple password authentication.

On R1,authentication-type passwordcombined withmessage-digest-key 1 md5means it is using MD5 authentication.

Critical point from Nokia SR OS OSPF Authentication Section:

“Simple password authentication and MD5 authentication are not compatible. Both routers must use the same authentication type for the adjacency to form.”

Thus, Router R1 has the incorrect authentication key type.

That’s why the correct answer is C.

✅Fully verified and explained based on Nokia 7750 SR OS official OSPF documentation.

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 (OSPF Database Exchange Logic):

If a router detects that its database contains a newer copy of an LSA than what its neighbor has advertised (lower sequence number seen in DBD packet), it sends a Link State Update containing the newer LSA back to its neighbor.

Thus, correct answer: A.

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Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (Link State Protocol Architecture):

Link state protocols (OSPF, IS-IS) maintain:

Neighbor (adjacency) database → tracks neighbors and adjacencies

Topology (Link State) database → entire area topology

Routing (Forwarding Information Base) derived from SPF calculations

Thus, correct answer is B.

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