Huawei Updated H12-891_V1.0 Exam Questions and Answers by stevie

Understanding SR-MPLS Label Calculation

SR-MPLS usesSegment Routing Global Block (SRGB)andPrefix SIDsto assign labels dynamically. TheMPLS labelfor a node’s loopback interface is calculated as follows:

MPLS Label=SRGB Base+Prefix SID Index

Where:

SRGB Base=20000(as given in the figure)

Prefix SID Index=30(configured for R3’s Loopback1)

Label Calculation:

20000+30=20030

Thus, theMPLS label corresponding to the loopback1 interface of R3 is 20030.

Why the Answer is 20030?

✔The SRGB defines the base label range.

✔Each router is assigned a unique Prefix SID index.

✔The label is dynamically computed by adding the Prefix SID Index to the SRGB Base.

Why Other Numbers Are Incorrect?

❌Any value outside the range 20000-21000

Would be incorrect because it must be withinR3’s SRGB range.

❌Using the Prefix SID Index directly (30)

Incorrect becauseMPLS labels are not assigned directly using Prefix SIDs; they are computed using the SRGB.

????Reference:Huawei HCIE Datacom – SR-MPLS Label Calculation and SRGB

The command port-isolate enable is used on Huawei switches to completely isolate traffic at both Layer 2 and Layer 3 between different interfaces within the same VLAN. This isolation prevents any communication between isolated ports—even if they belong to the same subnet or VLAN—making it a critical security feature in multi-tenant environments.

Usage Context:

Often used in shared service or hotel network scenarios.

Can be applied in access port configurations.

Does not require additional VLAN creation or private VLAN features.

Huawei Datacom Reference:

"To completely isolate Layer 2 and Layer 3 communication between interfaces in the same VLAN, run the port-isolate enable command under the interface view."

(Source: HCIE-Datacom Study Guide V3.0 – Chapter: VLAN & Security Technologies, Section: Port Isolation)

✅A. encoding: indicates the character set encoding format. Currently, only UTF-8 encoding is supported.

UTF-8 is the default and only supported character encoding in NETCONF XML.

✅B. /: indicates the end of the current tag.

In XML, closes an element, defining the end of a structure.

✅C.

The

✅D. ?>: indicates the end of an instruction.

Closes theXML declaration.

Reference from Huawei HCIE-Datacom Documentation:

Huawei NETCONF Development Guide – XML Formatting Rules

HCIE-Datacom Training Material – Understanding XML in Network Automation

ForOSPF neighbors to reach Full state, they must exchangeLSAs (Link State Advertisements) properlyand synchronize their databases.

Possible Causes Preventing OSPF from Entering Full State:

✅A. A link works abnormally

If thephysical or Layer 2 linkis unstable,OSPF Hello packetsmay be lost, preventing the Full state.

✅B. The OSPF network types on both ends of the link are inconsistent

OSPF network types (Broadcast, P2P, NBMA, etc.) must matchon both ends.

Example: If one router isP2Pand the other isBroadcast, adjacency issues occur.

✅C. The router IDs of neighbors are the same

Router ID conflicts prevent OSPF adjacencies from forming.

Each router must have aunique Router ID.

✅D. The OSPF MTU values of interfaces on both ends of the link are different

If MTU settings do not match,OSPF Database Description (DD) packets may be dropped, preventing Full state.

Reference from Huawei HCIE-Datacom Documentation:

Huawei OSPF Configuration Guide – Troubleshooting OSPF Neighbor Issues

HCIE-Datacom Study Material – OSPF Adjacency and Route Synchronization