Note: It's not a BT Router i'm using, i'm using a Netgear DG834N. I am sure BT Routers like the HomeHub have a MTU Size of 1500 set in the Router Interface, am I correct? My Netgear DG834N has a MTU Size of 1458 in the Router Interface by default. Thanks for responding.
The first MTU value is the interface MTU, it’s 1500 bytes by default for Ethernet. The second one is the IP MTU which is also 1500 bytes. Once you get above 1500 bytes your router will start fragmenting the IP packets. Is this limit of 1500 bytes really working? There’s an easy way to find out. Determine the MTU size of the LAN and WAN of a router $> ping –f –l (this is a lowercase “L”) [MTU size] [destination] How to check your LAN connection of your router to your computer: $> ping –f –l 1500 192.168.0.1. … How to Set Up PPPoE Internet Access - Lifewire May 09, 2020
However, if your Internet uplink only supports a lower MTU (e.g. 1492 bytes with PPPoE or L2TP) your router is forced to fragment each full-size packet that the server sends towards the Internet. To remove that additional processing and bandwidth overhead you can tell your server to reduce its interface MTU to (in that case) 1492.
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