H12-891_V1.0 Exam Dumps - Huawei HCIE-Datacom Questions and Answers

Understanding "Two-City Three-Center" Networking

????What is "Two-City Three-Center" Networking?

Ahigh-availability disaster recovery (DR) solutionused byfinancial institutions, government, and enterprise networks.

"Two cities"→ Indicates that data centers are deployed intwo different locationsfor redundancy.

"Three centers"→ Includestwo active data centers + one remote disaster recovery center.

Bearer WAN Layers in "Two-City Three-Center" Networks

✅A. Core Layer

Provides high-speed backbone connectivitybetween different data centers.

Useshigh-capacity routers and optical linksfor long-distance communication.

✅B. Aggregation Layer

Connects access sites to the core network.

Aggregates traffic frombranch offices, remote sites, and smaller data centers.

✅D. Access Layer

Connects end-users, remote branches, and applicationsto the WAN.

UsesCE (Customer Edge) routers and firewallsto ensure secure access.

❌C. Control Layer (Incorrect Choice)

The control plane exists in networking, but it isnot a physical bearer WAN layer.

The control layer is a logical function, not a network topology layer.

Real-World Application:

Banking Networks:Ensures thatcore banking applications remain available even in case of a disaster.

Government Data Centers:Enablescross-city data replication for public services.

✅Reference:Huawei HCIE-Datacom Guide – "Two-City Three-Center" Network Design

Comprehensive and Detailed In-Depth Explanation:

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.

Comprehensive and Detailed In-Depth Explanation:

AfterPortal authenticationon a wireless network, the following parameters can be used for authorization:

free-rule (A):Allows traffic even before authentication.

UCL (B):User Control List, specifying user permissions.

ACL (D):Access Control List, defining permitted or denied traffic.

TheIP address (C), however, isnot used as an authorization parameterdirectly. Instead, IP addresses are typically assigned after successful authentication, and the control policies are applied based on user profiles or access lists.

Understanding EVPN (Ethernet VPN) and ARP Request Handling

????What is EVPN?

EVPN (Ethernet VPN) is aBGP-based control plane for VXLANthat improvesLayer 2 & Layer 3 network scalability.

Eliminatesflood-and-learn behaviorusingBGP MAC/IP advertisement routes.

????Why is an ARP Request Sent?

WhenCE1 (192.168.1.1/24) wants to communicate with CE2 (192.168.1.2/24), it sends anARP requestto discover the MAC address of CE2.

????How Does EVPN Process the ARP Request?

1️⃣PE1 receives the ARP request from CE1.

2️⃣PE1 sends a MAC/IP advertisement route (Type 2 EVPN route) to inform PE2 and PE3 of CE1’s MAC address.

3️⃣PE1 forwards the ARP request as BUM (Broadcast, Unknown unicast, and Multicast) traffic to PE2 and PE3.

4️⃣PE3 (Designated Forwarder - DF) forwards the packet to CE2.

5️⃣PE2 (Non-DF) does NOT forward the packet to avoid loops.

Analysis of the Answer Choices:

✅A. When forwarding the packet to PE3, PE1 needs to add the BUM traffic label allocated by PE3 to the packet.

Correct:

BUM (Broadcast, Unknown Unicast, Multicast) traffic in EVPNis encapsulated with aspecial labelassigned by the receiving PE.

PE1adds the BUM traffic label for PE3before sending the ARP request.

✅B. PE1 sends a MAC/IP advertisement route carrying the MAC address of CE1.

Correct:

EVPN Type 2 MAC/IP advertisement routesare sent to inform other PEs of CE1’s MAC/IP binding.

❌C. PE2 forwards the packet to CE1.

Incorrect:

PE2 is the Non-Designated Forwarder (Non-DF)anddoes NOT forward BUM trafficto avoid loops.

✅D. PE3 forwards the packet to CE1.

Correct:

PE3 is the Designated Forwarder (DF) for this segment, meaning itforwards the ARP request to CE2.

Final Answer: A, B, D

✅Reference:Huawei HCIE-Datacom Guide – EVPN BGP MAC/IP Advertisement and BUM Traffic Handling

Real-World Application:

Data Center Interconnect (DCI):EVPN prevents excessiveARP floodingacross VXLAN networks.

Enterprise Campus Networks:UsesEVPN VXLAN to scale Layer 2 connectivity across multiple locations.

Comprehensive and Detailed In-Depth Explanation:

In MPLS (Multi-Protocol Label Switching), thelabel retention modedetermines how an LSR (Label Switching Router) handles labels received from its neighbors:

Liberal Mode:

An LSRretains all labels distributed by its neighbors, not just the labels from the next-hop LSR.

This approachensures faster convergencebecause the LSR does not need to request new labels if the next hop changes.

Itdoes not save memory or label space, as it stores more labels than strictly necessary.

Conservative Mode:

An LSRonly retains labels from its next-hop neighbors, saving memory and label space.

StatementsCandDare correct because they accurately describe liberal mode.

StatementsAandBare incorrect because they describe conservative mode.

Understanding 802.1X Authentication in Enterprise Networks

????What is 802.1X?

802.1X is a network access control (NAC) protocol that enforces authentication before allowing a device to connect to a LAN.

It usesEAP (Extensible Authentication Protocol)overRADIUSfor user verification.

Typically deployed incorporate and campus networksforsecure wired and wireless access.

????How Does 802.1X Work?

1️⃣Client (Supplicant) → Requests network access.

2️⃣Switch (Authenticator) → Forwards request to RADIUS server.

3️⃣RADIUS Server → Verifies credentials & grants access.

Mandatory Steps to Enable 802.1X on SW3

✅A. Configure an AAA Scheme

Defines authentication, authorization, and accounting (AAA) methods.

Links802.1X authentication to the RADIUS server.

✅B. Configure an Authentication Profile

Specifies how authentication is handled on the switch.

Associates802.1X authentication with an AAA scheme.

✅C. Configure an Authentication Domain

Groups authentication policies for different user types.

MapsAAA scheme to user login requests.

✅D. Configure an 802.1X Access Profile

Applies 802.1X authentication to specific switch ports (GE0/0/2 & GE0/0/3).

Ensures thatonly authenticated users can pass traffic.

Why Are All Four Steps Necessary?

✅Each step plays a critical role in enabling 802.1X authentication and linking it to the RADIUS server.

✅Without any one of these configurations, the 802.1X authentication process would fail.

Real-World Application:

Enterprise Wired Security:Ensures thatonly authenticated devicesaccess corporate networks.

University Campuses & Public Wi-Fi:Prevents unauthorized access tosecure LAN environments.

✅Reference:Huawei HCIE-Datacom Guide – 802.1X Authentication & RADIUS Server Configuration

Understanding HTTP/1.1 Response Headers

????What is an HTTP Response?

When a web server responds to an HTTP request, itsends an HTTP response message.

The response containsheaders, a status line, and a response body.

Elements of an HTTP Response Header:

✅A. Status Code→Correct

Indicates the response status (e.g., 200 OK, 404 Not Found).

✅B. Reason Phrase→Correct

Provides ahuman-readable explanationof the status code (e.g., OK, Not Found).

✅C. Protocol Version→Correct

Specifieswhich HTTP version is being used(e.g., HTTP/1.1).

❌D. Response Method→Incorrect

TheHTTP method (GET, POST, etc.) is part of the request, not the response.

BGP EVPN Type 2 Route (MAC/IP Advertisement Route)

This route carriesMAC and IP address bindingsto inform remote VTEPs about locally learned endpoints.

Why Use arp collect host enable?

Collects ARP entriesof locally connected hosts.

EnablesBGP EVPN Type 2 route generationto distribute the learned ARP information.

Incorrect Answer Explanations:❌A. mac-address xxxx-xxxx-xxxx– Manually configures a MAC address butdoes not enable ARP collection for EVPN Type 2 routes.❌B. arp-proxy enable– Enables ARP Proxy butdoes not advertise ARP information using BGP EVPN.❌D. arp distribute-gateway enable– Used inDistributed Anycast Gateway (DAG) modebutnot for collecting host ARP data.

Reference from Huawei HCIE-Datacom Documentation:

Huawei VXLAN EVPN Configuration Guide – ARP Handling and EVPN Type 2 Routes

HCIE-Datacom Training Material – VTEP ARP Advertisement in VXLAN Networks

Comprehensive and Detailed Explanation:

✔SRv6 (Segment Routing over IPv6) Flavorsprovide additionalprocessing behaviorsfor SRv6End instructions.

✔PSP (Penultimate Segment Popping) Flavor:

PSP enables the penultimate node to remove the SRH (Segment Routing Header)before forwarding the packet to the last segment.

This reduces the processing overheadon the final segment node.

✔Correct End Instructions for PSP:

✅(A) End.X→ Cross-connect behavior between segments.

✅(C) End.T→ Transport encapsulation in SRv6.

✅(D) End→ Basic SRv6 endpoint behavior.

❌(B) End.BM is incorrect→ This is used forBinding Segment (BSID)behavior and does not support PSP.

????Reference:Huawei HCIE Datacom – SRv6 Flavors and End Instructions

Correct Order for HTTP Request Line:

1. Request Method (e.g., GET, POST)

2. URI (Uniform Resource Identifier) (e.g., /index.html)

3. Protocol Version (e.g., HTTP/1.1)

Request Method

URI

Protocol Version

Comprehensive and Detailed Explanation:

Structure of an HTTP Request Message

An HTTP request message consists of:

1️⃣Request Line → Specifies the request method, the target resource (URI), andthe HTTP version.

2️⃣Headers → Provides additional request details (e.g., Host, User-Agent).

3️⃣Body (optional) → Used in methods like POST for sending data.

Format of an HTTP Request Line:

GET /index.html HTTP/1.1

GET → Request method

/index.html → URI (resource being requested)

HTTP/1.1 → Protocol version

Why Other Fields Are Incorrect?

❌Status Code → This belongs to an HTTP response, not a request.

❌Mixing Headers into the Request Line → Headers should be placed separately after the request line.