QUESTION: 13

On an IS-IS network, each router can generate LSPs.
Which of the following events trigger the generation of a new LSP?

Related IS-IS interfaces go up or down.
Periodic updates occur.
Inter-area IP routes change.
The IS-IS interface cost is increased.

Answer(s): A,B,D

Explanation:

LSP Generation in IS-IS
IS-IS routers generate new Link State Packets (LSPs) under the following conditions:

Interface Status Changes: When IS-IS interfaces go up or down, the link state changes, triggering LSP updates.

Periodic Updates: IS-IS periodically regenerates LSPs to ensure link-state information remains synchronized across the network.

Interface Metric Changes: Any modification to interface costs results in a new LSP to reflect the updated cost in the network.

Incorrect Option

C . Inter-area IP routes change is incorrect because IS-IS does not inherently differentiate between areas for LSP generation.

HCIP-Datacom-Core Reference

IS-IS LSP generation rules are detailed in the IS-IS configuration and implementation chapters.

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QUESTION: 14

Similar to the OSPF DR, the IS-IS DIS needs to be elected on a broadcast network. However, the OSPF DR is preemptive by default, whereas the IS-IS DIS is not preemptive by default.

TRUE
FALSE

Answer(s): A

Explanation:

DIS and DR Election

The IS-IS Designated Intermediate System (DIS) is responsible for generating and updating pseudonode LSPs on a broadcast network.

Unlike OSPF DR, the IS-IS DIS does not preempt by default. This behavior avoids unnecessary flapping in the network due to frequent DIS re-elections.

HCIP-Datacom-Core Reference

The characteristics of DIS and DR behavior are explained in IS-IS network operation chapters.

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QUESTION: 15

On an IS-IS network, routers send LSPs to exchange link state information. LSPs are classified into Level-1 LSPs and Level-2 LSPs and have the same format.
Which of the following parts constitute the LSP ID in an LSP?

LSP Number
Pseudonode ID
System ID
IS Type

Answer(s): A,B,C

Explanation:

IS-IS Overview: Intermediate System to Intermediate System (IS-IS) is a link-state routing protocol. Routers exchange Link State Packets (LSPs) to maintain a synchronized link-state database. These LSPs are categorized into Level-1 LSPs (intra-area routing) and Level-2 LSPs (inter-area routing). Both types share the same packet format.

Reference:

HCIP-Datacom-Core Technology Training Material (IS-IS LSPs and Packet Structure).

LSP ID Format: The LSP ID uniquely identifies each LSP and ensures accurate routing information. It comprises the following components:

System ID (C): A 6-byte identifier assigned to each router, derived from the router's NET (Network Entity Title). This identifier ensures unique identification of routers within the IS-IS domain.

Pseudonode ID (B): Assigned when a router acts as a Designated Intermediate System (DIS) on a broadcast network. It differentiates LSPs generated by the DIS from other routers.

LSP Number (A): A 1-byte field indicating the sequence number of the LSP. It helps distinguish multiple LSPs generated by the same router for the same level.

HCIP-Datacom Advanced Routing & Switching Technology (IS-IS LSP Format).

IS Type Exclusion:

IS Type (D) is not part of the LSP ID itself. It is a field within the IS-IS PDU that indicates the type of Intermediate System (Level-1, Level-2, or both) but does not contribute to the composition of the LSP ID.

HCIE-Datacom V1.0 Training Material (IS-IS Basics and Levels).

Conclusion: The LSP ID in IS-IS consists of System ID, Pseudonode ID, and LSP Number. These components uniquely identify each LSP within the IS-IS domain.

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QUESTION: 16

On an OSPF network, interfaces are classified into four types based on link layer protocols.
Which of the following types can interfaces on an IS-IS network be classified into based on physical links?

P2P
Broadcast
P2MP
NBMA

Answer(s): A,B

Explanation:

IS-IS Interface Types

IS-IS interfaces are categorized based on physical link characteristics:

Point-to-Point (P2P): Direct connections between two routers.

Broadcast: Shared medium networks where multiple routers communicate.

Incorrect Options

C . P2MP and D. NBMA are not standard interface classifications in IS-IS.

HCIP-Datacom-Core Reference

IS-IS physical link classifications are elaborated in IS-IS link configuration sections.

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QUESTION: 13

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