MTU stands for Maximum Transmission Unit, which is the largest amount of data that your broadband connection can handle at any given time. If there is too much data being sent at once, your router breaks it down into smaller packets to keep everything running smoothly.
If your MTU is set up incorrectly on your router, it can affect your broadband performance and cause issues with loading web pages and accessing certain websites, including secure sites (with https in the address).
If you're experiencing any of the above problems, it's a good idea to check your MTU.
If you've got a bOnline router, it should be automatically configured to 1432, which is the correct setting. However, if you're still experiencing problems you can try lowering it to 1400.
If you've got a bOnline Super Router, it will be automatically configured to 1500. This is the correct setting for Fibre and you shouldn't try to change it.