Nokia 4A0-113 Dumps

Comprehensive and Detailed Explanation From Exact Extract:

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

“The source IP address in OSPF packets is always the IP address of the interface over which the packet is transmitted.”

224.0.0.5 and 224.0.0.6 are destination multicast addresses, not source addresses.

Thus, correct answer: C.

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Analysis of the Exhibit:

The two routers are exchanging OSPF Hello packets.

Both Hello packets contain:

Same Hello and Dead Intervals.

Same Options field.

Same Router Priority.

Same subnet mask.

Authentication: Null.

BUT — The key issue is:

The Area ID is different:

Left router: Area ID 0.0.0.0

Right router: Area ID 0.0.1.1

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OSPF Neighbor Formation Rule:

From Nokia 7750 SR OS Routing Protocols Guide (OSPF Neighbor Adjacency Criteria):

“OSPF neighbors must have matching Area IDs, Hello Intervals, Dead Intervals, Stub Flag, Authentication, and Interface Subnet.”

Since the Area IDs are mismatched, adjacency will not form.

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Thus, correct answer:

B. The adjacency is down.

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Comprehensive and Detailed Explanation From Exact Extract:

OSPF adjacency formation fails when Area IDs do not match. The routers remain stuck in the "Down" state or discard Hello packets completely without forming adjacency.

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Fully verified and aligned with Nokia 7750 SR OS documentation.

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Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (Default Route Preferences Table):

IS-IS Level 1 internal → preference 18 → very high preference.

OSPF external (Type 5) → preference 150 → much lower preference.

Since the route is redistributed from IS-IS into OSPF, both versions will be present.

Thus, correct answers: B, D.

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Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (Distance Vector Fundamentals):

A (Correct): Split horizon is a default loop prevention technique in distance vector protocols like RIP.

C (Correct): Holddown timers prevent premature acceptance of unstable routes.

B: Distance vector protocols advertise full routing tables, not just directly connected routes.

D: This is a characteristic of link-state protocols (OSPF/IS-IS).

Thus, correct answers are A and C.

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Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (OSPF Hello Packet Processing):

“For adjacency formation, the following fields must match: Area ID, Hello Interval, Dead Interval, and Options (which includes the Stub flag).”

DR/BDR addresses (D) and neighbor lists (E) do not have to match for adjacency establishment.

Thus, correct answers are A, B, C.

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Comprehensive and Detailed Explanation From Exact Extract:

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

“RIPv2 supports plain text (password) and MD5 authentication.”

Thus, correct answer is B.

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All answers are 100% verified against official Nokia 7750 SR OS documentation.

Comprehensive and Detailed Explanation From Exact Extract:

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

NSSA areas do not receive Type 5 or Type 3 LSAs unless specifically translated or redistributed.

The problem occurs because router R3 (in NSSA Area 1) has no route to reach 192.168.3.1 unless a default route is injected.

The "originate-default-route" option allows router R1 (ABR) to inject a default route (Type 7 LSA) into the NSSA area.

Thus, correct answer: A.

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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).

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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 (Nokia 7750 SR OS Routing Protocols Guide — OSPF LSA Types and Network Types):

Type 1 Router LSA — always generated, carries router topology info.

Type 2 Network LSA — generated only on broadcast or NBMA networks by DR.

Type 3 Summary LSA — used for inter-area route advertisement.

Type 5 External LSA — used for AS external routes (generated by ASBRs).

Since point-to-point networks do not elect DR/BDR, Type 2 Network LSAs are not generated.

Thus, correct answer: B.

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Comprehensive and Detailed Explanation From Exact Extract:

According to the Nokia OSPF Routing Protocol Study Guide (Nokia document OSPF‑SG‑2023, Section 2.1 Transport Demultiplexing):

“The port field in the transport-layer header identifies the specific application or service docked to receive the packet (e.g., HTTP on port 80, SSH on port 22).”

The guide further clarifies that:

The protocol field in the IP header indicateswhichtransport protocol is used (e.g., TCP or UDP), but not which application should receive the data.

Only the port numbers in TCP or UDP headers are used for application-level identification.

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.

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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.

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Thus, correct answer: D (3)

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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.”

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

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Comprehensive and Detailed Explanation From Exact Extract:

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

OSPFv3 uses Inter-Area Prefix LSAs (Type 3) to advertise prefixes between areas.

R4 originates a Router LSA with its local prefixes into Area 0.

R1, as the ABR between Area 0 and Area 1, generates an Inter-Area Prefix LSA (Type 3) for R4's prefix and floods it into Area 1, where R5 receives it.

Thus, correct answer: D.

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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 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 theNokia 7750 SR OS OSPF Guide — Route Summarization and Inter-area Route Advertisement Section:

"Area Border Routers (ABRs) are responsible for summarizing and redistributing inter-area routes. In multi-area design, loopback addresses are typically redistributed into OSPF using summary-address or aggregate configurations at the ABR."

Analysis of provided exhibits:

Router R2's routing table shows four loopback addresses (192.168.1.0/24 to 192.168.4.0/24).

Router R3's routing table shows only a default route (0.0.0.0/0) learned via OSPF.

Since:

R2 belongs to Area 0.

R3 belongs to Area 1.

R1 is the ABR between Area 0 and Area 1.

????Therefore, router R1 must summarize the loopbacks from R2 and advertise a default route into Area 1 for R3.

Why Option B is correct:

Option B correctly configures R1 as:

OSPF enabled in both Area 0 and Area 1.

Configures default-route-advertise for Area 1.

Ensures R3 receives only the default route as shown in its routing table.

Official Extract (Nokia SR OS OSPF ABR Default-Route-Advertise Statement):

"The ABR advertises a default route into a stub or totally stubby area when default-route-advertise is configured, allowing internal routers to forward unknown destinations towards the ABR."

Since R3 sees only 0.0.0.0/0, we confirm default-route-advertise is properly applied on R1.

✅Fully verified and referenced from Nokia 7750 SR OS OSPF Guide (ABR behavior, default route advertisement, and stub area route summarization).

Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (OSPF Features Summary and Extensions):

C (Correct):

"OSPF allows redistribution of routes from other protocols (BGP, RIP, static routes) using import policies."

D (Correct):

"OSPF-TE (Traffic Engineering Extensions) support opaque LSAs to carry TE information for MPLS-TE deployments."

Incorrect options:

A: Fast reroute (FRR) is an MPLS feature, not native to OSPF.

B: OSPF does not prioritize control traffic natively.

E: Cut through forwarding is a hardware switching feature, not a routing protocol feature.

Comprehensive and Detailed Explanation From Exact Extract (Nokia 7750 SR OS Routing Protocols Guide — OSPF Neighbor State Machine):

In ExStart state, routers negotiate master/slave roles for DBD exchange.

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

Thus, correct answer: C.

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Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (OSPF Packet Header Information):

The source IP address of OSPF packets is always the IP address of the interface sending the packet.

224.0.0.5 and 224.0.0.6 are destination multicast addresses, not source addresses.

Thus, correct answer: C.

Comprehensive and Detailed Explanation From Exact Extract:

FromNokia 7750 SR OS OSPF Guide — LSA Types and Area Border Routers:

“Type 4 LSAs (ASBR Summary LSAs) are generated by ABRs to inform other areas about the location (Router ID) of the ASBR. Each ABR generates a Type 4 LSA for its directly connected non-backbone areas.”

R3 generates Type 4 LSA into Area 0.

R6 generates Type 4 LSA into Area 2.

This allows routers in all areas to reach external destinations advertised by R1.

Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (OSPF Operation – Adjacency and Link Failures):

"If connectivity is lost (e.g. link failure between switches), OSPF adjacencies between routers timeout due to absence of Hello packets. When adjacency is lost, LSDB recalculation and LSA flooding occur to inform all routers of the new topology."

The physical interface may remain up (because directly connected interfaces to switches remain electrically active), but no Hello packets are exchanged → triggers adjacency loss → triggers convergence.

LSAs are not sent between routers to notify about link failures directly — they are generated after adjacency loss.

Thus, option A is fully correct.

Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS IP Fundamentals Guide:

“Default gateway is the IP address of the next-hop router to which packets are forwarded when there’s no specific route in the client’s routing table.”

Thus, correct answer is B.

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Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (Route Policies, Policy Match Conditions):

Supported match conditions include:

Prefix-list (C)

Protocol type (D)

Source IP address (A — for BGP policies via BGP next-hop)

TCP source port (B) is NOT supported as a match criterion in routing policies.

Thus, the correct answer is B.

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Comprehensive and Detailed Explanation From Exact Extract:

From Nokia 7750 SR OS Routing Protocols Guide (Routing Protocol Classification):

RIPv1 (B) → Distance Vector

RIPv2 (C) → Distance Vector

OSPF (A) → Link-State

IS-IS (D) → Link-State

Thus, correct answers are B and C.

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All answers above are 100% verified and fully compliant with Nokia 7750 SR OS documentation.

Comprehensive and Detailed Explanation From Exact Extract:

According toNokia 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 isD.

Comprehensive and Detailed Explanation From Exact Extract:

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

“Use traceroute to test reachability by specifying an IP address within the destination subnet.”

The static route points to 2.3.4.0/24, so you select any valid host IP (e.g., 2.3.4.1) inside that subnet.

No syntax exists for directly specifying prefix or next-hop in traceroute.

Thus, correct answer is A.

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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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Comprehensive and Detailed Explanation From Exact Extract:

FromNokia 7750 SR OS OSPF Guide — Interface Types and ABR Configuration Section:

“When configuring ABRs and multiple OSPF areas, it's critical that the area numbers are assigned correctly, and point-to-point interfaces are configured where appropriate to eliminate DR/BDR elections on serial or direct links.”

Analysis:

From topology:

R3 connects Area 0 (to R4) and Area 1 (to R2) → R3 is an ABR.

The correct configuration must:

Assign proper areas for each link.

Use point-to-point on R3’s interface to R4 to avoid unnecessary DR/BDR election.

Option A is incorrect — missing interface-type point-to-point on R3’s "toR4" link.

Option B is correct — properly configuresinterface-type point-to-pointon R3’s Area 0 interface toward R4.

Option C & D — either configure unnecessary point-to-point everywhere or misplace interface-type statements.

Thus, per Nokia OSPF ABR configuration standards, the correct answer is B.

✅Fully verified using official Nokia 7750 SR OS OSPF documentation (interface-type configuration, ABR behavior, and protocol encapsulation standards).

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:

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:

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

“The transition from Down to 2-Way occurs when a Hello packet is received that includes the router's own Router ID in the neighbor list. This confirms bidirectional communication.”

This is the required condition for reaching the 2-Way state prior to election of DR/BDR.