Problem Occurs When the EG8141A5 Port Is Configured to Work in Bridging Mode

Hi friend.

The ONT eth port by default works in L2. Just need to keep the ONT port as default settings and configure native VLAN for the ONT eth port from the OLT. 

You could use the ont port native-vlan(gpon) command to configure a local VLAN for an ONT Ethernet port. This command is used to configure the default VLAN for the ONT port. Assume that the native VLAN function is enabled. For inbound untagged packets, the system applies native VLAN tags to the packets. For outbound packets with native VLAN tags, the system strips the VLAN tags off the packets. The default native VLAN is VLAN 1.

Reference below command to configure native vlan for the ont eth port:

huawei(config-if-gpon-0/3)#ont port native-vlan
{ portid<U><0,15> }:1
{ ontid<U><0,127> }:0
{ eth<K>|iphost<K>|moca<K>|vdsl<K>|wifi<K> }:eth
{ ont-portid<U><1,24> }:1
{ priority<K>|vlan<K> }:vlan
{ vlanid<U><0,4095> }:100
{ <cr>|priority<K> }:
Command:
ont port native-vlan 1 0 eth 1 vlan 100

For more details, please click: 

ont port native-vlan(gpon)

Thanks.