Huawei H12-821_V1.0 Practice Test - Questions Answers, Page 2

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.

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.

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.

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.

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.

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.

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.

Mandatory BGP Attributes

Next_Hop: Specifies the next hop to reach the destination.

AS_Path: Lists the autonomous systems traversed, crucial for loop prevention and route selection.

Optional Attributes

MED (Multi-Exit Discriminator) and Local_Preference are optional attributes that aid in route preference but are not mandatory.

HCIP-Datacom-Core Reference

BGP attribute behavior and classifications are detailed in BGP path selection principles.

Non-Client Definition in IBGP

In an IBGP setup with a Route Reflector (RR), a non-client is an IBGP peer that is neither the RR itself nor its client.

Non-clients must establish fully meshed IBGP connections with all other non-clients and the RR because IBGP rules prohibit route propagation between non-clients without a direct connection.

HCIP-Datacom-Core Reference

The behavior of non-clients in an RR topology is clearly outlined in the BGP implementation chapters.

BGP Keepalive Message Behavior

Keepalive messages are used to maintain the Established state of a BGP peer relationship.

The Keepalive timer determines the frequency of these messages and defaults to 60 seconds, as per the BGP specification.

HCIP-Datacom-Core Reference

The Keepalive timer default value is covered in the BGP configuration and operational principles.

Export Routing Policy Changes

When an export routing policy is modified, BGP does not automatically resend affected routes. Manual intervention, such as a clear ip bgp command, is required to resend Update messages reflecting the new policy.

Incorrect Options

B . IGP routes can also be advertised into BGP using redistribution, not just the network command.

C . A router can be configured with multiple BGP processes using different AS numbers (multi-instance BGP).

D . Open messages carry additional parameters such as AS number, Hold Time, and Router ID, not just the header.

HCIP-Datacom-Core Reference

BGP policy and update behavior are detailed in the route control and redistribution chapters.