Mikrotik RB951ui-2hnd Native&access via one wire, how?

Question

Mikrotik

Hello. I'm in pain for a few days.
There is a need for MikroTik RB951ui-2hnd rOS 6.44.5 to accept 2 VLANs.
1 - Vlan 1226 works in access mode for a while until we understand what the problem is
2- Vlan 621 works in native mode.
The wire from the provider goes to ether1, a white ip (Vlan1226) physically hangs on it, we tried to distribute Vlan621 using a switch-chip - ZERO, using a bridge - ZERO.
Can someone give the logic of Vlan operation in MikroTik, is it possible to receive native and access at the same time and transfer the trunk to another port, or do I need to tell the provider to also throw Vlan1226 into native and dance with the trunk and scatter both Vlans on Mikrotik.

Answer 1

one of the vlans must be tagged. and it should be accepted tagged. and to which switch in Mikrotik you will bind your business.
better to provide config

Answer 2

access vlan - port operation mode, in which the tag is removed from the vlan and it is returned without a tag. Used on access to connect
native vlan equipment - all packets in which the vlan tag is not specified are sent to this vlan in the trunk. Those. this is actually an untagged vlan in the trunk port.
And now please tell us how you can separate two untagged vlans in one port?