Figure 1 shows the actual networking.
Figure 1 Networking
IS-IS transmits BPDU packets whose MAC address is in 0180-C2##-####-#### format. BPDU packets are reserved multicast packets at the link layer and need to carry VLAN tags when transparently transmitted by the DSLAM. IS-IS Hello packets do not carry VLAN tags when being transmitted through Layer 3 GE interfaces; therefore, the DSLAM fails to transparently transmit IS-IS Hello packets. The PON interface receives no IS-IS Hello packet from the peer end, so the PON interface fails to establish the neighbor relationship.
To address this problem, configure the GE interface as a subinterface which allows packets to carry VLAN tags so that the DSLAM can transparently transmit these packets.
The DSLAM adds VLAN tags to packets sent by a PON interface.