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

TheTime-To-Live (TTL) fieldin MPLS is essential forpreventing infinite loopsandenhancing security.

MPLS TTL Field Functionality:

It prevents packets fromcirculating indefinitelyin the MPLS network.

It allowstraceroute (tracert) to identify MPLS hopswhen TTL propagation is enabled.

Explanation of Correct Answers:✅B. The processing of IP TTL copy hides the LSR in an MPLS domain, improving security.

IfTTL propagation is disabled, MPLS routers do not decrease TTL, hidinginternal LSRsfrom traceroute, enhancing security.

✅C. MPLS provides two TTL processing modes:

Default Mode:The MPLS TTLcopies the IP TTL valuewhen an IP packet enters the MPLS network.

Uniform Mode:The ingress LERsets the MPLS TTL to 255, so it does not decrement.

✅D. MPLS encapsulation in frame mode supports the TTL field, while cell mode does not.

Frame Mode (Ethernet, PPP, etc.) supports TTL.

Cell Mode (ATM/MPLS) does not support TTL.

Incorrect Answer Explanation:❌A. If TTL copy is disabled, users can use the tracert function to view MPLS hops.

Wrong!If TTL propagation is disabled, tracertcannotsee LSRs inside the MPLS core network.

Reference from Huawei HCIE-Datacom Documentation:

Huawei MPLS Technology Guide – TTL Field & Loop Prevention

HCIE-Datacom MPLS VPN Configuration Guide – Traceroute in MPLS Networks

Comprehensive and Detailed Explanation:

✔Huawei OPS (Open Programmability System)followsRESTful API principles, usingHTTP methodsfor device management.

✔HTTP Methods Used in OPS:

✅GET→ Retrieves data from the device.

✅POST→ Creates new data/configurations.

✅PUT→ Replacesentire configuration objects.

✅PATCH→Updates specific fieldsof a configuration object.✅(Correct Answer)

SincePATCH is used for modifying specific values in managed objects, the correct answer isD.

????Reference:Huawei HCIE Datacom – RESTful API Operations in Huawei OPS

Why is Free Mobility Not Based on VLANs or IP Addresses?

Free mobilityin Huawei CloudCampus implementspolicy-based user access controlbased onuser identity (rather than VLANs or IP addresses).

Users canmove across different network locationswhile maintaining their assignedsecurity and access policies.

✅How Free Mobility Works:

Policies are applied based onUser Groupsinstead of VLAN or IP.

UsesGroup-Based Policy Control (GBP)andSoftware-Defined Access (SDA)principles.

❌Incorrect Statement Explanation:

Traditional networks rely on VLANs and IP addresses for segmentation, butFree Mobility applies policies at the user level, allowing seamless access anywhere on the network.

Reference from Huawei HCIE-Datacom Documentation:

Huawei CloudCampus Solution Guide – Free Mobility and Policy Control

HCIE-Datacom Training Material – Identity-Based Networking

Comprehensive and Detailed Explanation:

✔gRPC supports four types of RPCs:

Unary RPC→ Client sendsonerequest, server respondsonce.

Server streaming RPC→ Server sendsmultiple responses.

Client streaming RPC→ Client sendsmultiple requests.

Bidirectional streaming RPC→Bothsides exchange multiple messages.

✔Why B and C Are Incorrect:

❌(B) Incorrect→ The method rpc dataPublish(stream serviceArgs) returns(stream serviceArgs) {} violates gRPC syntax.

❌(C) Incorrect→ rpc stream LotsOfGreetings(HelloRequest) returns (HelloResponse) {} containsincorrect stream positioning.

????Reference:Huawei HCIE Datacom – gRPC API and Streaming Mechanisms