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

Type C dual-homing provides device-level protection with two OLTs; when one OLT/uplink fails, services switch to the peer OLT. In single-homing, ONUs are associated with only one OLT; therefore an OLT failure interrupts services (C). Single-homing has simpler networking and management than dual-homing (D). It does not offer switchover to another OLT (so B is incorrect), and the “important-service” positioning in A is typically applied to dual-homing scenarios that require the highest availability.

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.

Huawei GPON implements hierarchical traffic control. CAR (Committed Access Rate) can be applied at multiple layers: GEM-port level (GEM-CAR), per-flow (Flow-CAR), and T-CONT level (T-CONT-CAR) for upstream bandwidth policing/shaping and guaranteeing QoS. GEM mapping is a classification/association mechanism (service → GEM/T-CONT) rather than a traffic-control action, so it is not a CAR measure.

In AQM, high-priority queues are given more tolerant (larger) thresholds so they are less likely to be dropped early. Setting a smaller early-drop threshold for high priority would increase their loss probability, which contradicts QoS objectives—thus A is incorrect. Descriptions in B, C, and D align with Huawei’s treatment of congestion avoidance: RED/WRED proactively drops to stabilize queues and can reduce delay variation; tail drop at full buffer can lead to global TCP synchronization.

Type C GPON protection uses two different OLTs (dual-home). With uplink status linkage configured, a failure of the active OLT itself or its uplink interface triggers a protection switchover to the standby OLT to maintain service continuity for ONUs homed through the protected ODN.

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.

On Huawei access devices/OLTs, VoIP/H.248 setup typically includes:

In voip view, configure media IP with gateway:

ip address media – e.g., ip address media 10.10.10.10 10.10.10.1.

Configure signaling IP without a gateway parameter:

ip address signaling – e.g., ip address signaling 10.10.10.10.

Add/enter the H.248 interface and apply properties with if-h248 attribute ….

It’s common to reset/enable the MG interface after attribute changes; many guides show reset coldstart (or reset) issued under the H.248 interface to activate the interface.

Authoritative configuration examples show media takes an IP and gateway, but signaling takes only the IP. Therefore, option D (attempting to configure signaling with a gateway parameter) is incorrect. Options A and C match documented syntax and workflow. Option B reflects the documented practice of issuing a reset (often written as reset coldstart) under the H.248 interface to apply/enable, as shown in Huawei-focused configuration guides.

Standard OTDR operation allows you to configure multiple acquisition parameters:

Measurement range (distance range): sets the maximum span to be traced; best practice is typically 1.5–2× the fiber length under test.

Wavelength: select test wavelength(s), e.g., 1310/1550 nm for SM fiber, to observe different loss characteristics.

Mode: vendors provide real-time/average (or similar) acquisition modes to stabilize traces.

Pulse width: controls dynamic range vs. event resolution; longer pulses see farther but increase dead zones, while shorter pulses improve resolution at the cost of range.

These are documented in foundational OTDR references and application notes.

Huawei OLTs support ONT replacement without deleting the original service profile by using ONT replace/auto-find mechanisms. The OLT can bind the new ONT (new SN) to the existing ONT configuration template (service-port, VLAN, QoS, multicast profile, etc.), achieving a smooth replacement without manually removing and re-creating the ONT and services. The statement that you must remove the ONT and re-register from scratch is therefore wrong.

XGS-PON downstream line rate is ~10 Gbit/s. When 12 terminals share a PON tree concurrently, the rough per-terminal share is 10,000 Mbit/s ÷ 12 ≈ 833 Mbit/s, commonly expressed as “about 800 Mbit/s.” This aligns with planning examples in HCIP-Access where downstream concurrency on XGS-PON is calculated by dividing the port rate by the number of active ONUs/APs on the splitter.

In IP multicast, only one copy per multicast group (program) is forwarded upstream, regardless of how many users are watching it. Replication happens downstream at the access/edge, not toward the core. Therefore the upstream traffic equals the number of active multicast groups × per-group bitrate:

20 programs × 2 Mbit/s = 40 Mbit/s.

This behavior is consistent with Huawei’s multicast feature descriptions and general multicast principles (IGMP/PIM), which explain that multicast traffic is sent as a single flow per group and replicated only where branching occurs, not multiplied by user count.

In 10G-EPON (IEEE 802.3av), the wavelength plan uses 1577 nm downstream and 1270 nm upstream. The 1270 nm upstream is used in both asymmetric and symmetric 10G-EPON profiles.

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.

In FTTB/C voice access with SIP, typical “off-hook but no tone/voice” faults are caused by signaling/control path or device status issues: abnormal MG (Media Gateway/H.248/SIP) interface state on the ONU, unreachable routing between ONU and IMS/softswitch, or a voice server outage. These directly prevent registration, call setup, or media negotiation, resulting in no tone or no audio.

Generic “upper-layer packet loss” on the OLT uplink is not a standard, deterministic root cause specifically for off-hook immediate sound failure; minor loss does not inherently suppress locally generated tones and is not listed as a primary cause in Huawei voice troubleshooting guidance.

SNMPv2c uses a community-string model (clear-text “read”/“write” strings) and provides no authentication integrity or encryption. Only SNMPv3 adds auth/privacy (AuthNoPriv/AuthPriv) with hashing and encryption. Therefore, stating that SNMPv2c can encrypt user passwords is false.

In campus/access QoS planning on Huawei devices, queue scheduling commonly supports RR, WRR/DRR, and (optionally) strict-priority. WRR (Weighted Round Robin) assigns larger weights to high-priority queues so they receive more transmission opportunities and bandwidth than lower-priority queues while still serving all queues. Therefore, when ensuring better treatment for high-priority services under round-robin–type scheduling, WRR is the recommended choice.

Huawei access security recommends limiting MAC learn counts per port/VLAN, and using anti-MAC-spoofing bindings: either automatic (dynamic) bindings generated by the system or manual static MAC bindings to the service/port. Simply replacing a terminal is not a network-side mitigation method and is not listed as a protection measure.

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.

In NGN architectures, services (voice, video, data) converge over a packet-based backbone. The core switching layer provides the unified transport using IP/MPLS and related QoS mechanisms, delivering high reliability and large-capacity switching for all upper-layer services. The control and management layers orchestrate services, while the edge/access layer aggregates users—but the packet-based integrated transmission platform itself is the role of the core.

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.

With PITP enabled and Vendor-tag switching allowed, Huawei OLTs support transparent transmission and augmentation: the OLT keeps the user-carried Vendor tag and appends the local Vendor tag (e.g., slot/port/location), ensuring the upstream AAA/BRAS receives both the access-side identity and the OLT’s own location identity. Simply adding only the local tag (A) loses user-side info; forwarding unchanged (B) omits OLT location; discarding (D) contradicts the feature intent.

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.

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.

Type B provides redundancy with two OLT PON ports on the same OLT and two feeder (backbone) fibers to the ODN. Therefore it protects the PON ports and the backbone/feeder path. It does not protect the OLT itself (still a single OLT) and does not protect the ONU branch fibers.

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.

In GPON Type C dual-attribution protection, the ONU has dual PON connections to two OLT PON ports (or two OLTs). When the protection group is configured to track the OLT’s uplink Ethernet port, a Down state on that uplink is an OLT-side trigger. The OLT initiates the protection action (forces the working/standby role swap via PON protection signaling).

A — Correct behavior: After the OLT triggers protection, the ONU’s working PON interface becomes standby, and the protect interface becomes working.

B — Correct behavior: The OLT monitors and updates the ONU uplink status as part of the protection group state machine.

C — Correct behavior: After inversion, services egress the ONU via the protect PON port toward the OLT, i.e., traffic follows the configured protect path.

D — Incorrect (answer): In this scenario the trigger is the OLT’s uplink Ethernet status, not an ONU-detected failure. Therefore the ONU does not detect the fault nor initiate the switchover; the OLT does.

(Reference: HCIP-Access V2.5 – GPON protection mechanisms; Huawei OLT protection group behavior, Type C dual-homing with uplink-tracking.)

The OLT’s anti–IP-attack (control-plane protection) function identifies and rate-limits abnormal or attack traffic to protect the CPU. It does not block legitimate management protocols such as Telnet/SSH by design. Remote management remains available when sourced from permitted hosts and within configured thresholds; administrators can also use trusted-host/ACL policies if needed.

Huawei anti-DoS on access boards performs periodic detection. Ports with consecutive detections of abnormal traffic are placed into a blacklist/quarantine state. The system then applies a random back-off interval before re-detecting; if no further anomalies are found, the port can be automatically removed from the blacklist.

Drag & Drop Answer (NGN layers → devices):

Network control layer → Softswitch

Service management layer → OSS system

Edge access layer → MA5800

Core switching layer → Core router

Why:

Softswitch handles call/session control ⇒ control layer.

OSS provides O&M/service management ⇒ service management layer.

MA5800 is an OLT/access device ⇒ edge access layer.

Core router provides backbone forwarding ⇒ core switching layer.

For OLT uplink (NNI) protection groups (timedelay/weight, etc.), Huawei requires that each physical port belongs to one protection group only to avoid conflicting switchover control. A member port cannot be part of multiple protection groups simultaneously.