Guide: How to Increase EC2 Instance MTU (Jumbo Frames)

This guide summarizes the process for increasing the Maximum Transmission Unit (MTU) size for your EC2 instances to enable jumbo frames, based on the Tutorials Dojo article and supplemented with Windows instructions.

What is MTU and Why Increase It?

The Maximum Transmission Unit (MTU) of a network connection is the size of the largest permissible packet that can be passed over the connection. Anything larger must be broken down into smaller fragments, which can add latency.

Jumbo frames refer to Ethernet frames with a payload larger than the standard 1500 bytes. By increasing your EC2 instance's MTU to support jumbo frames (typically to a value of 9001), you can send larger packets.

The primary benefit: For traffic within a VPC, using jumbo frames can reduce network overhead and increase throughput, leading to better performance for network-bound applications.

Important Considerations

• Scope: Jumbo frames are for traffic inside your VPC. All traffic over an Internet Gateway, VPC peering connection, or VPN connection is limited to an MTU of 1500.

• Instance Support: Not all instance types support jumbo frames. All current generation instance types do.

• Path MTU Discovery (PMTUD): It's important that hosts along a network path agree on an MTU. If a host sends a packet that is too large for an intermediate host to handle, an ICMP error message (Destination Unreachable: Fragmentation Needed) is returned.

Part 1: How to Configure MTU on Linux

The following steps use standard Linux networking commands to check and set the MTU.

Step 1.1: Check the Path MTU with tracepath

Before making changes, you can verify the maximum supported MTU between two instances within your VPC.

1. Install tracepath if needed:

   • Ubuntu/Debian: sudo apt install iputils-tracepath

   • Amazon Linux/CentOS: sudo yum install iputils

2. Run the command from your source instance to the destination instance's private IP: