MTU - default interface MTU

The default value of the MTU for an Ethernet interface is always 1500 bytes. This is the case regardless of the type or speed of Ethernet used.

This standard has remained consistent, and it is a convention that’s been carried forward to faster speeds for compatibility reasons. When moving up in speeds to 10, 40, and even 100 Gbps, the conventional MTU is still 1500, but it is typically best practice at these speeds to use jumbo frames, which can be in excess of 9000 bytes. This makes communications much more efficient especially in datacenter scenarios where higher speeds are the norm.

When considering the MTU size, the platform and software being used must be taken into account.

However, using a larger MTU size also means that if a packet is lost or corrupted, more data will need to be retransmitted, which can lead to inefficiencies. Therefore, for most home and office networks, a smaller MTU size of 1500 is used to balance efficiency and reliability.

Links

https://forum.networklessons.com/t/mtu-troubleshooting-on-cisco-ios/1078/211?u=lagapides