What is the default MTU size?

Answered by Tom Adger

The default MTU size, which stands for Maximum Transmission Unit, is typically set to 1500 bytes. This size is commonly used in most networks and is considered the standard or normal MTU size.

The MTU size refers to the largest amount of data that can be transmitted in a single network packet without fragmentation. It is an important parameter in network communication as it affects the efficiency and performance of data transmission.

The choice of 1500 bytes as the default MTU size is not arbitrary, but rather a result of historical and technical considerations. In Ethernet networks, for example, the MTU size of 1500 bytes has been widely adopted. This size was initially chosen to accommodate the header and trailer overhead of Ethernet frames, which typically adds 14 bytes for the Ethernet header and 4 bytes for the frame check sequence (FCS) trailer.

By using a default MTU size of 1500 bytes, network devices can efficiently transmit data without the need for fragmentation, reducing overhead and improving overall network performance. This size has proven to be suitable for most common network applications and provides a balance between efficiency and compatibility.

It is worth mentioning that in some cases, particularly in specialized network configurations or for specific use cases, a larger MTU size may be preferred. This is often referred to as jumbo frames, and a common choice for a larger MTU size is 9000 bytes.

Using a larger MTU size like 9000 bytes can potentially increase network throughput and reduce the overhead associated with smaller packets. However, it is important to note that using jumbo frames requires support from all network devices along the transmission path, including routers, switches, and network interface cards. Additionally, jumbo frames may not always be compatible with all network protocols and applications.

The default MTU size is commonly set to 1500 bytes, providing a balance between efficiency and compatibility in most network environments. However, for specific use cases or specialized configurations, a larger MTU size such as 9000 bytes may be chosen to optimize network performance.