H35-211_V2.5 Exam Dumps : HCIP-Access V2.5

A single-layer VLAN is limited by the IEEE 802.1Q VLAN ID space (1–4094), i.e., about 4K VLANs. In large PON deployments, when you must separate multiple services (e.g., HSI, VoIP, IPTV) and the user scale approaches or exceeds the 4K ceiling, a dual-layer VLAN (QinQ) design is required to extend the VLAN namespace and implement hierarchical isolation (access VLAN + service/aggregation VLAN).

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.

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.