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

Comprehensive and Detailed Explanation:

✔ Paramiko is a Python library that provides SSH and SFTP functionality.✔ The SFTPClient class is specifically designed for SFTP (Secure File Transfer Protocol) operations.

✔ How It Works:

A Transport session is established using Transport().

An SFTP session is created using SFTPClient.from_transport().

File operations (upload/download) are performed via SFTP methods.

✔ Why Not Other Options?❌ (A) Packetizer class → Handles low-level SSH message processing, not SFTP.❌ (C) Channel class → Creates SSH channels, not SFTP sessions.❌ (D) Transport class → Establishes SSH connections, but does not perform file operations.

???? Reference: Huawei HCIE Datacom – Python Paramiko and SFTP Implementation

Comprehensive and Detailed Explanation:

✔ The Best Protection Against MITM and Spoofing Attacks:✅ (D) Associating DHCP Snooping with IPSG (IP Source Guard) and DAI (Dynamic ARP Inspection) provides complete protection by:

Blocking rogue DHCP servers.

Preventing MAC/IP spoofing.

Ensuring only valid clients access the network.

✔ Why Not Other Options?❌ (A) Configuring trusted/untrusted interfaces only helps block rogue DHCP servers, but does not prevent spoofing.❌ (B) Limiting MAC address learning prevents MAC flooding, but does not stop MITM attacks.❌ (C) Checking the CHADDR field in DHCP Snooping helps detect spoofed requests, but does not block all MITM scenarios.

???? Reference: Huawei HCIE Datacom – Security Mechanisms for Intranet Protection

Understanding SRLB (Segment Routing Local Block)

???? What is SRLB?

SRLB (Segment Routing Local Block) is a range of local MPLS labels used by Segment Routing (SR-MPLS).

These labels are only relevant to the local router and are not advertised to other routers.

???? Key SR-MPLS Label Blocks:✅ SRGB (Segment Routing Global Block) – Globally significant labels shared among routers.✅ SRLB (Segment Routing Local Block) – Locally significant labels, not shared.

Why is the Answer TRUE?

✅ SRLB labels are only locally defined and are NOT distributed via IGP (OSPF or IS-IS).✅ They are used for local forwarding decisions within an SR-enabled router.✅ Only SRGB labels are advertised to ensure consistent global label assignment.

Real-World Application:

Traffic Engineering (TE): Uses SRLB for custom local path optimizations.

Segment Routing Networks: Ensures scalable MPLS forwarding without requiring full LDP signaling.

✅ Reference: Huawei HCIE-Datacom Guide – Segment Routing Label Blocks (SRGB & SRLB)

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