Pass the Huawei HCIE-Datacom H12-891_V1.0 Questions and answers with ValidTests

Understanding VGMP (Virtual Gateway Management Protocol)

????What is VGMP?

VGMP (Virtual Gateway Management Protocol) is used in Huawei firewalls to manage hot standby (HRP - Hot Standby Routing Protocol).

Ensures that theactive and standby firewalls synchronize their statesfor high availability.

????How Does VGMP Work?

TheActive and Standby firewalls exchange VGMP packetsto maintain state synchronization.

These packets are encapsulatedwithin UDPfor transport.

Thedefault UDP port for VGMP is 512.

Why is the Answer 512?

✅Huawei firewalls use UDP port 512 by default for VGMP communication.

✅This ensures that VGMP heartbeats and synchronization messages are correctly processed.

Real-World Application:

Enterprise Firewalls:VGMP ensuresfailover between active and standby firewalls.

Carrier-Grade Firewalls:UsesVGMP with HRP to achieve zero-downtime firewall redundancy.

✅Reference:Huawei HCIE-Datacom Guide – VGMP and HRP High Availability Mechanisms

Comprehensive and Detailed In-Depth Explanation:

TheStrict Priority (SP) scheduling algorithmalways gives preference to high-priority queues.

A:Correct. SP scheduling may lead toqueue starvationbecause low-priority queues might never get serviced if high-priority traffic is constant.

B:Correct. SP always schedules thehighest-priority queue first.

C:Correct. Among multiple low-priority queues, if SP is combined with FIFO (First In, First Out), packets that arrive first are forwarded first.

D:Incorrect. The SP algorithmdoes not guarantee minimum bandwidthfor lower-priority queues. It prioritizes high-priority queues regardless of bandwidth configuration, which can lead to starvation of lower-priority traffic. To ensure minimum bandwidth, aWeighted Fair Queuing (WFQ)orCBWFQ (Class-Based Weighted Fair Queuing)algorithm would be more suitable.

SRv6 Policies can be:

Statically configured via CLI on routers.

Dynamically generated and delivered from a controller such as Huawei iMaster NCE for centralized path computation.

This dual approach allows flexibility in deployments.

Exact Extract – Huawei SRv6 Deployment Guide:

“SRv6 Policies can be locally configured or dynamically delivered via PCEP from the controller, enabling both static and SDN-based implementations.”

Comprehensive and Detailed Explanation:

Key Factors Affecting FTP Performance:

Tail Drop and TCP Synchronization (A)✅

Tail Dropcauses TCPglobal synchronization, reducing FTP speeds drastically when congestion occurs.

Since FTP isTCP-based, packet loss due to tail drop forcesTCP retransmissions, further degrading performance.

Priority Preemption by Video Traffic (D)✅

UDP-based real-time video trafficis often prioritized overTCP-based trafficto avoid jitter and packet loss.

If video traffic hashigher QoS priority, FTP bandwidth may bepreempted, leading toslow speeds.

Incorrect Options:

❌Option B:PQ scheduling typically prioritizes latency-sensitive traffic (VoIP), but this scenario does not mention priority queuing for FTP.

❌Option C:No information about an explicitrate limiton FTP traffic.

????Reference:Huawei HCIE Datacom – QoS and Congestion Control

Comprehensive and Detailed In-Depth Explanation:

During a network migration test, it is crucial not only to verify that the network itself is functioning correctly but also to ensure thatupper-layer application servicesare running properly on the newly migrated network. Migration testing aims to confirm that the transition has not disrupted service functionality.

Option A and C focus solely on network performance, which is necessary but insufficient.

Option B refers to command outputs, which are technical checks and do not guarantee service continuity.

Option D correctly identifies that successful migration is indicated byproper operation of upper-layer application services, as the primary purpose of a network is to support these applications.

Understanding the Command Components:

This is aHuawei CLI commandused fordiagnosing connectivitywithin aVPN instancein an MPLS network.

ping -aX→ Specifies thesource IP address(X) of the ping packets.

-cY→ Specifies thenumber of ICMP Echo Request packetsto send (Y).

-sZ→ Defines thesize (in bytes) of each ICMP Echo Requestpacket (Z).

-vpn-instance M→ Specifies theVPN instance (VRF) Mto which the ping packets belong.

Why are all options correct?

✅A. The source IP address of the ping packets is X.

The -aX optionforces the ping to originate from IP Xinstead of the default interface IP.

✅B. The ping packets belong to VPN instance M.

The -vpn-instance M optionensures the ping is sent within VPN instance M, allowing verification ofMPLS L3VPN routing.

✅C. During the ping operation, the quantity of ICMP Request packets is Y.

The -cY parameter sets thenumber of ICMP Echo Requeststo be sent, making Y the total count.

✅D. The size of each ICMP Request packet for the ping operation is Z bytes.

The -sZ parameterdefines packet size, helping to testMTU (Maximum Transmission Unit)issues.

Real-World Application:

Verifying MPLS VPN connectivity:Ensure customer networks are reachable withinseparate VRFs.

Testing MTU & fragmentation:Using -sZ, operators can check ifpacket fragmentationoccurs.

Debugging asymmetric routing issues:By forcing -aX, engineers can trace return paths.

✅Reference:Huawei HCIE-Datacom Official Guide – MPLS VPN Troubleshooting & Ping Options

InOSPFv3,Link-LSA (Type 8)is generated by a routerfor each of its interfacesto advertise:

Therouter's link-local addresson that interface.

TheIPv6 prefixesassociated with the interface.

Flags and options, such as router priority or loopback indicators.

From the output:

Link-LSA (Interface GigabitEthernet0/0/0)

Originating Router: 10.1.2.2

Link-Local Address: FE80::2E0:FCFF:FECD:4F79

Prefix: 2001:DB8:2345:23::/64

A. The link-local address of R2’s GE0/0/0 is FE80::2E0:FCFF:FECD:4F79→ This matches the Link-Local Address field in the LSA.✅

B. The IPv6 address prefix of R2’s GE0/0/0 is 2001:DB8:2345:23::/64→ This matches the Prefix field in the LSA.✅

C. This LSA indicates that R2 does not support external routes but can participate in IPv6 route calculation→❌Incorrect.

TheLink-LSAdoesnot provide any indicationabout external route capabilities.

It simply advertisesinterface-specific IPv6 and link-local info.

Whether R2 supports external routes depends onType 5 (External) or Type 7 (NSSA) LSAs, not Link-LSAs.

D. This LSA is generated by R2→ The Originating Router: 10.1.2.2 is R2’s router ID, so this LSA is definitely generated by R2.✅

Correct Answers:A, B, D

The Link-LSA in OSPFv3 contains:

The link-local address used by the originating router on the link.

A list of all IPv6 prefixes associated with the link.

Flags such as router priority and the Router-LSA options.

These LSAs are alwaysgenerated by the router itselfand arenot flooded beyond the link.

Understanding Inter-AS MPLS VPN Option C (Solution 2)

In MPLS L3VPN Inter-AS Option C, the Route Reflectors (RRs) are used for VPN route distribution but do not participate in data forwarding. The traffic forwarding path is based on MPLS labels assigned at different routers.

Each data packet carries two MPLS labels:

Transport Label (T1) – Used for forwarding within the backbone.

VPN Label (V1) – Used for VPN route identification.

Breaking Down the Labels:

✔VPN Label (V1) – Allocated by PE1 (Answer: C✅)

V1 (Inner Label) is the VPN label assigned by the egress PE router (PE1).

This label ensures that when the packet reaches PE1, it knows how to forward the traffic to CE1 (192.168.1.1).

✔Transport Label (T1) – Allocated by P2 (Answer: B✅)

T1 (Outer Label) is the transport label assigned by P2 to forward the packet across the AS core.

This label ensures the packet reaches the next-hop router (ASBR-PE1 in AS100).

Why Are the Other Options Incorrect?

❌A. "T1 is allocated by RR2" (Incorrect)

RR2 is used only for route reflection; it does not participate in label allocation or forwarding.

❌D. "V1 is allocated by P2" (Incorrect)

P2 is an intermediate router and does not allocate VPN labels.

VPN labels are always assigned by the egress PE router (PE1 in AS100).

????Reference:Huawei HCIE Datacom – MPLS L3VPN Inter-AS Option C