Hello everyone my I know what is the meaning of this error and how to fix this error?
Thank you in advance.

The problem is exactly what is writed on the mesage, ask your ISP because you receive Router Advertisements with 2000 MTU…
Or if you have another router before the MikroTik one, disable RA, or set the Router Advertisements on that router, not on MikroTik, with the rigth MTU size of 1500.
Hi sir rextended,
Thank you for the quick response. I have to study or research
about MTU, because i have no knowledge about that. Thank you once again