H12-891_V1.0 Exam Dumps : HCIE-Datacom V1.0

Comprehensive and Detailed In-Depth Explanation:

In MPLS (Multi-Protocol Label Switching), thelabel retention modedetermines how an LSR (Label Switching Router) handles labels received from its neighbors:

Liberal Mode:

An LSRretains all labels distributed by its neighbors, not just the labels from the next-hop LSR.

This approachensures faster convergencebecause the LSR does not need to request new labels if the next hop changes.

Itdoes not save memory or label space, as it stores more labels than strictly necessary.

Conservative Mode:

An LSRonly retains labels from its next-hop neighbors, saving memory and label space.

StatementsCandDare correct because they accurately describe liberal mode.

StatementsAandBare incorrect because they describe conservative mode.

Ethernet Segment Identifier (ESI) is a 10-byte identifier used in EVPN (Ethernet VPN) to uniquely identify an Ethernet segment across a network, particularly in multi-homing scenarios. It ensures loop prevention and redundancy.

Exact Extract - HCIE-Datacom EVPN Section:

“The ESI is a 10-byte identifier and must be unique across the entire EVPN network. It plays a key role in identifying Ethernet segments in multi-homed environments.”

To analyze this question, let's break down the key concepts and the given LSDB (Link State Database) information from the figure:

Understanding the LSDB Output:

The output shows the OSPF LSDB on R2 with Router ID 10.1.123.2.

Area 0.0.0.0 (Area 0) is displayed along with several Link State Advertisements (LSAs) including Router LSAs, Network LSAs, and Summary LSAs.

Area 0.0.0.1 (Area 1) also displays Router LSAs and a Type 7 LSA (NSSA LSA) with Link-State ID 0.0.0.0.

An External LSA (Type 5) with Link-State ID 0.0.0.0 and AdvRouter 10.1.123.2 is also present.

Analysis of Each Option:

Option A: Area 1 is an NSSA.

Correct.

The presence of a Type 7 LSA (NSSA LSA) in the database indicates that Area 1 is configured as an NSSA (Not-So-Stubby Area).

NSSA allows the injection of Type 7 LSAs for external routes while blocking Type 5 LSAs from entering the area.

Option B: R2 translates Type 7 default route into Type 5 default route.

Correct.

In an NSSA, if an ABR (like R2) has the NSSA ASBR capability, it will convert Type 7 LSAs to Type 5 LSAs before injecting them into the backbone area (Area 0).

In the LSDB, we see both a Type 7 LSA (NSSA) and a corresponding Type 5 External LSA, confirming that R2 performs this translation.

Option C: R2 advertises the default route in the OSPF process.

Incorrect.

There is no indication that R2 itself is originating the default route.

The Type 7 LSA in Area 1 and the Type 5 LSA in Area 0 only indicate translation from another source, not R2 advertising it directly.

Option D: Area 1 does not have Type 3 LSAs. The possible cause is that R2 filters Type 3 LSAs in the outbound direction of Area 1.

Incorrect.

In an NSSA area, Type 3 LSAs (Inter-Area Prefix LSAs) are typically not generated for external routes.

The absence of Type 3 LSAs in Area 1 is due to the nature of NSSA itself rather than any filtering configured on R2.