MTU settings rely on your network’s traits and your applications. Balance efficiency and reliability when choosing a value that works across your network devices and links. Tips for choosing the best MTU:
The standard 1500-byte MTU suits most networks and apps, being typical for Ethernet and the Internet. If there’s no specific need, sticking with this default works well.
For bandwidth-intensive apps like video streaming, gaming, or VoIP, consider upping the MTU for faster data flow. But ensure all network parts support it to dodge packet loss or fragmentation, which can harm data quality.
To gauge the max supported MTU, tools like ‘ping’ or ‘traceroute’ with ‘-f’ (do not fragment) and ‘-l’ (packet size) options help. For instance, test the MTU between your PC and the switch:
ping -f -l 1500 <switch IP address>
If you get a reply, 1500 bytes MTU works. If it says “Packet needs to be fragmented but DF set,” 1500 is too big. Reduce till you get a response. The sweet spot is the largest MTU without causing fragmentation.
For error-sensitive apps like file transfers, VPNs, or encryption, consider lowering the MTU to cut packet loss and fragmentation risks that lead to delays or data errors.
Yet, avoid going too small. A very tiny MTU can slow data flow by increasing header overhead and packet count. The best MTU is the smallest without harming performance.
In a diverse network setup with various device MTUs, aim for an MTU that suits all to avoid packet loss or fragmentation that impacts data reliability.
For instance, if a switch (MTU 1500) connects to a router (MTU 1400), set the switch’s MTU to 1400 or less. If not, the router fragments packets larger than 1400 bytes. Alternatively, features like MSS Clamping or Path MTU Discovery on the router adjust packet MTUs based on the network path.
Read more: How to Troubleshoot Common MTU Issues