H35-211_V2.5 HCIP-Access V2.5 Questions and Answers

Huawei devices support independent mapping/remarking for inner and outer VLAN priorities (802.1p CoS) when QinQ is used. Operators can define distinct mapping tables or remark rules per tag. Option A is incorrect (priorities can be derived or remarked, not “must be” tag-in-packet), option C is incorrect because mapping profiles are configurable, and option D confuses VLAN IDs with priorities; inner/outer CoS can be mapped independently for inbound/outbound directions.

With ONT Zero-Touch Provisioning (ZTP) enabled on eSight, newly discovered ONTs can be automatically identified and provisioned by pushing service templates from eSight. This removes the need for advance (preset) service configuration on the OLT during incremental onboarding; the OLT simply accepts the provisioning delivered by eSight.

For intercommunication across VLANs—especially for voice between ONUs—ARP Proxy is configured on the OLT so the OLT responds to ARP on behalf of endpoints and bridges traffic across VLAN boundaries without exposing the full L3 gateway to each segment.

A: “Saving IP addresses” is not the defining difference; ARP Proxy’s function is ARP mediation to enable L2/L3 reachability.

B: Both features target intercommunication, not isolation.

D: A VLAN service-profile is planned and applied from the OLT side to ONUs; it is not “configured on the ONU” directly for this purpose.

In eSight’s ONT Zero-Touch workflow, multi-service profiles define service parameters delivered to ONTs—primarily service VLANs such as Internet/Data VLAN, Voice VLAN, and IPTV/Multicast VLAN with related QoS. Hardware attributes like ONU type or Ethernet port count are part of the device/ONT profile, not the multi-service profile. A generic “Default VLAN” parameter is not used here; instead, explicit service VLANs are specified (for example, data VLAN and voice VLAN).

The ONT details pane in eSight displays access-port attributes (admin/state, type), Ethernet rate/speed/duplex, and PON optical module telemetry such as temperature and Tx/Rx optical power for condition monitoring and troubleshooting.

In IEEE 802.1AX/802.3ad LACP operation, timeout detection relies on a multiplier of three consecutive LACP intervals. In short-timeout mode, the default period is ~1 s; if 3 intervals pass without receiving LACPDUs, the peer is considered expired and the member is removed (treated as Down for aggregation). Huawei implements this standard behavior for port-member validity in an Eth-Trunk.

(Reference: HCIP-Access V2.5 – Link Aggregation/LACP timers and member aging; IEEE LACP short-timeout 3× interval rule.)

Huawei Anti-MAC-Spoofing binds the source MAC to the service flow/port to prevent address forgery. It is functionally exclusive with certain per-VLAN MAC check features (e.g., WMAC, SC, PPPoe-SMAC) to avoid conflicting validation logic. For IPoE users with fixed IP, operators typically configure static bindings/entries so that address and access policies remain consistent.

Option D is wrong: disabling Anti-MAC-Spoofing and removing fixed entries can affect service behavior; if forwarding is interrupted, that does impact user service—so the statement is self-contradictory and incorrect.

IPTV over FTTH relies on multicast control; therefore the essential U2000 template is the IGMP template, which defines IGMP behaviors, program authorization binding, and multicast parameters used by the OLT/ONT. MGC applies to voice (VoIP), and SNMP pertains to NMS communication rather than IPTV service logic; value-added templates are not mandatory for basic IPTV.

A: Incorrect — RADIUS typically uses UDP (1812/1813), while HWTACACS/TACACS+ uses TCP (port 49).

B: Incorrect — In RADIUS, only the user-password attribute is encrypted; fields are not selectively encrypted by user choice. TACACS+ can encrypt the entire payload.

D: Incorrect — Because RADIUS uses UDP, transport is not inherently reliable.

C: Correct — RADIUS and HWTACACS differ in message structure and returned attributes after authentication (e.g., RADIUS attribute–value pairs for access control/QoS/VLAN vs. HWTACACS command/privilege oriented responses). Thus the returned content/format differs between the two.

Per RFC 3261 (SIP), “The CSeq header field of the response MUST equal the CSeq field of the request.” CSeq carries a sequence number and the method, thereby associating a response with the specific request it answers. While Call-ID ties together all messages within the same dialog, it does not identify the specific request/response pairing; CSeq does. Therefore, CSeq is the correct header for correlating a response to the exact request.

In Huawei access network devices (such as MA5800, EA5800, and SmartAX series), the DHCP Option 82 (Relay Agent Information Option) feature is used to identify the source location of DHCP requests coming from users connected to access ports.

This helps the DHCP server assign IP addresses based on access topology information, such as slot, port, and VLAN IDs.

When Option 82 is enabled globally and within the VLAN service profile, and the port/service-port is configured to allow user-side packets to carry Option 82, the device processes incoming DHCP requests as follows:

If a user-side DHCP packet does not contain Option 82:→ The device automatically adds local Option 82 information (e.g., circuit ID, remote ID) before forwarding it to the DHCP server.

If a user-side DHCP packet already contains Option 82:→ The device removes (strips) the existing Option 82 field to prevent spoofing or inconsistent location data.→ Then it adds its own local Option 82 information (accurate relay agent data based on the device’s configuration).→ The modified packet is then forwarded to the DHCP server.

This ensures that only trusted network-side Option 82 data is passed along, maintaining accurate user-location binding for IP address management and security.

Therefore, the correct behavior is:

The access device strips the Option 82 field from the user packet and adds its own local Option 82 information.

References (Aligned with HCIP-Access V2.5 and Huawei Technical Documents):

HCIP-Access V2.5 Study Guide – “Huawei Campus Network Overview” Chapter, Section: DHCP Relay and Option 82 Mechanism

Huawei MA5800/EA5800 Configuration Guide – IP Service → DHCP Relay and Option 82 Configuration

Huawei Enterprise Networking Product Documentation: “Understanding DHCP Option 82 Processing”

Huawei Access Network Feature Guide, Section: Processing Policies of DHCP Packets with Option 82

OLT-level (device-level) protection is achieved by dual-homing ONUs to two independent OLT interfaces so that services can switch to another OLT when one fails. In Huawei protection taxonomy, the dual-homing scheme (as contrasted with single-homing) provides device-side redundancy for the OLT. By comparison, Ethernet port protection groups and LACP protect uplink links and bandwidth at Layer 2, not the OLT device itself; single-homing does not protect against OLT failure.

10G-EPON is designed for coexistence with EPON on the same ODN by using separate downstream wavelengths and dual-rate upstream mechanisms. Operators can realize a smooth upgrade at the OLT (local end) by inserting WDM mux/demux modules (or using dual-rate PON ports) while continuing to use the existing ODN fiber plant and splitters. This is a standard migration path emphasized in HCIP-Access materials for PON evolution.

When the number of access users approaches or exceeds the single-layer VLAN space and services must be distinguished per user, Huawei recommends hierarchical VLAN (QinQ) on the uplink: map a customer VLAN (C-VLAN) at the access side and add a service/provider VLAN (S-VLAN) toward the aggregation/core, i.e., C → S+C. This expands scalability beyond the ~4K single-VLAN limit while enabling precise user/service binding for large FTTH deployments (e.g., ~5K users under one OLT).

Huawei’s alarm reference for PON ports lists the common possible causes of LOS (the OLT does not receive the expected optical signal) as:

The port laser is shut down;

The backbone optical fiber connected to the port is faulty;

All the ONTs/ONUs connected to the port are powered off or faulty;

(and potentially) port hardware faults.

These map directly to options D, B, and C. A rogue ONU generates specific “rogue ONU” alarms and is characterized by continuous/abnormal upstream emission; it is not a typical root cause of an LOS condition, which indicates absence of expected optical signal.

In Huawei QoS processing, traffic classification on access devices/OLTs can match Layer-3 and Layer-2 priority indicators and MPLS labels. Common match fields include IP DSCP (or IP precedence in the ToS byte), MPLS EXP, and IEEE 802.1p CoS carried in VLAN tags. These fields are used to place packets into scheduling/queuing behaviors and policing profiles.

IP multicast is designed for one-to-many delivery, allowing a single source stream to be replicated in the network only where branching is required. Compared with sending multiple unicast copies, multicast significantly reduces bandwidth consumption on shared links and provides efficient point-to-multipoint distribution. This is the core rationale for using multicast in video/TV services on campus and access networks.

Live TV uses multicast, while VOD uses unicast. If VOD works but live TV is a black screen, typical causes are multicast service-path/config mismatches or priority starvation for multicast control/traffic:

C: If the ONU uses different VLANs for VOD and live but the OLT has only one video service flow, multicast frames will not match the correct service-port, causing black screen.

D: A low-priority traffic profile for multicast join/report or stream on the OLT uplink may drop IGMP joins or multicast packets under load, resulting in black screen while unicast VOD still passes.

Queue scheduling choices such as PQ or DWRR (A/B) are generic congestion schemes; by themselves they are not direct root causes of a live-only black screen unless mis-classified, whereas C and D are recognized multicast-specific fault points.

In an H.248 (Megaco) control model, the MGC is the controller that issues provisioning/connection-control commands such as Add, Modify, Subtract, AuditValue, AuditCapabilities to the MG. The MG (Media Gateway) can initiate only specific messages toward the MGC to announce state changes or report detected events—namely ServiceChange (to indicate restart, failure, availability changes, etc.) and Notify (to report observed events collected per event descriptor). Therefore, among the listed options, the commands that the MG itself can send are ServiceChange and Notify.

For Huawei uplink protection (STH-NNI port protection) with workmode timedelay, the mandatory steps are:

Create/define the protection group with the protect-target and workmode timedelay;

Add member ports with roles (work/protect);

Enable the protection group.

Interface-level timers like offline-tx-off-time under the physical interface are not required for standard timedelay protection operation and are therefore optional.

A persistently high CPU on the OLT main control board is typically driven by excessive control-plane load or abnormal traffic patterns. Common causes include:

Illegal login attempts generating authentication and logging overhead (A)

Layer-2 loops leading to storms and protocol churn (B)

DoS/scan/attack traffic stressing control/management processing (C)

Rogue/misbehaving ONUs causing frequent state changes, registration flaps, or abnormal report traffic (D)

All listed factors are recognized contributors to elevated CPU on access OLTs.

On Huawei OLTs, the standard QoS pipeline for upstream packets is: first perform traffic classification (identify flows), then marking (set CoS/DSCP as required), next apply traffic policing (rate-limit and color traffic), followed by congestion avoidance (AQM such as RED/WRED), and finally congestion management (queue scheduling/priority queuing). This ordered sequence ensures correct identification and marking before any rate enforcement, and that packets encounter AQM prior to scheduler-based dequeue.

IPv4 multicast (historically “Class D”) occupies the address block 224.0.0.0 through 239.255.255.255. Any upper bound of 238.255.255.255 is incorrect because it excludes the full 239/8 administratively scoped range. This is standardized in the IANA IPv4 Multicast Address Space registry and reflected in foundational multicast specifications.

On Huawei OLTs (e.g., MA5600T/MA5680T), deploying IPTV/multicast commonly uses a program list (channel list) to map program numbers to multicast group addresses—this is configured with igmp program. When programs are statically configured under the multicast VLAN, the program definitions themselves are mandatory; without them, set-top boxes cannot select (zap to) channels by program number/address mapping and the OLT cannot correctly forward the requested multicast streams.

In GPON protection schemes, Type B (dual-homing to the same OLT) provides redundancy by using two PON ports on the same OLT (working/standby) and a redundant feeder path via a 2×N splitter or equivalent ODN design. Thus, the protection covers the OLT PON interfaces and the feeder fiber segment. It does not provide protection for the branch (distribution) fibers from the splitter to the ONUs, and it does not involve dual OLTs—that is the scope of Type C.

According to IEEE 802.3av wavelength planning adopted by Huawei 10G-EPON, downstream uses 1577 nm and 10G upstream uses 1270 nm. In asymmetric coexistence, 1G-EPON upstream uses 1310 nm, but for 10G-EPON upstream specifically the wavelength is 1270 nm. Therefore the correct upstream wavelength for 10G-EPON is 1270 nm.

Huawei access devices apply a deterministic service-flow match order for upstream user packets. VLAN-based matching is attempted first. If no specific service flow matches and TLS (Transparent LAN Service) is configured, the system falls back to the TLS service flow as the default L2 transparent handling for that port/user, ensuring service continuity without explicit per-VLAN bindings.

Terminal (ONT/ONU/CPE) selection adheres to engineering principles: align model and interfaces with the deployment mode and scenario, evaluate TCO/cost, and satisfy special requirements (such as PoE, Wi-Fi specs, voice/FXS, industrial temperature). Ignoring project requirements is contrary to standard design workflows; therefore D is not correct.

In Huawei’s 10G GPON (Gigabit-capable Passive Optical Network) system, different optical wavelengths are used for upstream and downstream transmission to ensure bidirectional communication over a single fiber.

According to the ITU-T G.987.x series and Huawei’s Access Network Technical Documentation, the wavelength plan for 10G GPON (XG-PON) is as follows:

Downstream (OLT → ONU): 1577 nm

Upstream (ONU → OLT): 1270 nm

This separation of wavelengths allows both transmission directions to occur simultaneously using WDM (Wavelength Division Multiplexing) on the same optical fiber, minimizing interference.

Huawei OLTs such as the MA5800 and EA5800 series follow this standard exactly — supporting 10G GPON (XG-PON) with downstream at 1577 nm and upstream at 1270 nm.

Hence, the correct answer is 1577 nm.

Answer: B

References (Aligned with HCIP-Access V2.5 and Huawei Technical Sources):

HCIP-Access V2.5 Study Guide – “Huawei Campus Network Overview” Chapter, Section: PON Technology Overview

Huawei 10G GPON (XG-PON) Technical White Paper

ITU-T G.987.2: 10-Gigabit-capable Passive Optical Networks (XG-PON): Physical Media Dependent (PMD) Layer Specification

Huawei MA5800 Product Description – 10G GPON Port Wavelength Specifications

Huawei eSight supports multiple L3/L2 discovery mechanisms:

Network-segment (subnet) scanning;

ARP-based discovery in broadcast domains;

Routing-table discovery to traverse multi-segment networks.

Administrators can configure an exclusion list of subnets/IPs; during discovery, eSight skips any addresses listed there, preventing unwanted polling/Onboarding.

Right. The SIP Max-Forwards header limits how many SIP elements a request can traverse. Each proxy decrements the value by one; when it reaches zero, the message must not be forwarded, preventing infinite loops and yielding responses like 483 (Too Many Hops). RFC 3261 (Sections 8.1.1.6, 16.6, 20.22) defines this behavior; later work further discusses loop mitigation