Huawei H12-891_V1.0 Exam Dumps

Comprehensive and Detailed In-Depth

By default, OSPF does not automatically associate a domain ID with a process ID. The concept of 'domain ID' is primarily used when redistributing routes between OSPF and BGP, particularly in MPLS VPN scenarios. The domain ID in OSPF helps maintain loop prevention and correct route advertisement between different OSPF domains. You can manually configure the domain ID using the domain-id command within the OSPF process view, but it is not inherently set to the process ID.

Huawei HCIE Datacom Official Certification Guide

Huawei OSPF Configuration and Maintenance Guide

===========

Comprehensive and Detailed

gRPC supports four types of RPCs:

Unary RPC Client sends one request, server responds once.

Server streaming RPC Server sends multiple responses.

Client streaming RPC Client sends multiple requests.

Bidirectional streaming RPC Both sides 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) {} contains incorrect stream positioning.

Reference: Huawei HCIE Datacom -- gRPC API and Streaming Mechanisms

For SRv6 (Segment Routing over IPv6) deployment on a bearer WAN, the following are essential:

IGP (OSPFv3 or IS-IS): Required for SID advertisement and SRv6 route computation

BGP: Required when deploying inter-domain SRv6 or for control plane distribution of VPN/service routes

Not required:

MPLS: SRv6 replaces MPLS labels with IPv6-based SIDs

BGP-LU: Used in MPLS-based inter-AS scenarios, not applicable to SRv6

Correct answers: B, C

VRRP (Virtual Router Redundancy Protocol) and Flapping

VRRP ensures gateway redundancy by allowing multiple routers to work together as a virtual router. Flapping occurs when the master and backup routers frequently switch roles.

Causes of VRRP Flapping:

A. Too small interval between Advertisement packet transmissions -- Can cause flapping

If the Advertisement interval is too short, frequent VRRP state changes can occur.

C. Packet loss on an interface of the backup device -- Can cause flapping

If the backup router loses VRRP packets, it might assume the master is down and initiate an election.

D. Flapping on the link transmitting VRRP Advertisement packets -- Can cause flapping

If the link used for VRRP experiences instability, packets may be lost, triggering VRRP role changes.

Incorrect Answer

B. Inconsistent preemption delay settings -- Does NOT cause VRRP flapping

Preemption delay only affects when a router takes over as master after recovering from a failure.

It does not directly cause flapping because the role change happens only after a delay, preventing frequent transitions.

Reference from Huawei HCIE-Datacom Documentation:

Huawei VRRP Configuration Guide -- Preventing VRRP Flapping

HCIE-Datacom Study Material -- VRRP Timers and Stability

Route Target (RT) is a BGP extended community attribute used in MPLS Layer 3 VPNs (L3VPNs) to control the import and export of VPN routes between different VPN instances (VRFs).

Explanation of Correct Answers:

A. Each VPN instance is associated with one or more pairs of VPN Target attributes, used to control VPN routing information advertisement and reception between sites.

Each VRF (VPN Routing and Forwarding instance) has an associated RT that determines which routes are imported and exported between VPNs.

RTs enable inter-VPN communication while maintaining separation between VPN customers.

B. Export Target and Import Target are independent of each other and support multiple values to implement flexible VPN routing information advertisement and reception control.

The Export RT specifies which routes should be advertised.

The Import RT specifies which routes should be accepted into a VRF.

These can be configured independently to control traffic flow between VPNs.

C. RTs are classified into two types: Export Target and Import Target.

Export Target: Defines which VPN routes are advertised.

Import Target: Defines which VPN routes are accepted.

A VPN instance can have multiple RTs to allow flexibility.

D. The RT value is advertised to neighbors through the BGP extended community attribute in Update messages.

RTs are carried in BGP UPDATE messages as part of the BGP extended community attribute, enabling VPN route exchange between PEs.

Reference from Huawei HCIE-Datacom Documentation:

Huawei MPLS VPN Configuration Guide -- Route Target (RT) Concepts

HCIE-Datacom Study Material -- BGP Route Advertisement in MPLS VPNs