When the default MTU value of the network interface cannot meet requirements (such as traffic mirror), you need to manually modify the network interface's MTU value.

danger

Unless necessary, do not modify the MTU value. This is because modifying the ENI MTU value may cause data to be fragmented or dropped.

Procedures

CenOS

Ubuntu

Windows

Taking CentOS 7.9 as an example, the procedure is as follows:

Run the ifconfig command to view the ENI MTU value. The output should be similar to the following figure:

Execute the following command to set the MTU value for Network Interface eth0.

mtu=<MTU值>
echo "${mtu}" > /sys/class/net/eth0/mtu
echo "echo \""${mtu}"\" > /sys/class/net/eth0/mtu">> /etc/rc.d/rc.local && chmod +x /etc/rc.d/rc.local

Example configuration in this topic:

Execute ifconfig command to check if it takes effect. The output should be similar to the following figure:

Taking Ubuntu Server 16.04 LTS and Ubuntu Server 18.04 LTS as examples, the procedure is as follows:

Execute ifconfig to check the Network Interface MTU value. The output should be similar to the following figure:

Setting the MTU value on different Ubuntu versions.

Ubuntu Server 16.04 LTS

Execute the following command to create a script file.

vim /etc/network/if-up.d/setmtu

Press i to enter edit mode, then enter the following content to set the MTU value.

#!/bin/sh
ifconfig <网卡名称> mtu <MTU值>

The figure demonstrates:

#!/bin/sh
ifconfig eth0 mtu 1000

Press esc key to exit edit mode, then press :wq to save changes and exit.

Run the following command to grant execute permission to the setmtu file.

chmod +x /etc/network/if-up.d/setmtu

Run the reboot command to restart the ECS.

Execute ifconfig command to check if it takes effect. The output should be similar to the following figure:

Ubuntu Server 18.04 LTS

Run the vim /etc/netplan/50-cloud-init.yaml command, press i to enter edit mode, and enter the following configuration:

network:
version: 2
ethernets:
eth0:# 本文示例为eth0
dhcp4: true
match:
macaddress: 00:16:3e:5e:**:**
mtu: <MTU值> # 本文示例为1000
set-name: eth0

Press esc key to exit edit mode, then press :wq to save changes and exit.

Run netplan apply command to restart the network service and apply the configuration.

Execute ifconfig to check the Network Interface MTU value. The output should be similar to the following figure:

Taking Windows Server 2016 as an example, the steps are as follows:

On the Windows desktop, click Start > Windows PowerShell to open Windows PowerShell.

Run the following command to view the Network Interface name.

netsh interface ipv4 show subinterfaces

The output is as follows:

Run the following command to modify the Network Interface MTU value.

netsh interface ipv4 set subinterface "网卡名称" mtu=1399 store=persistent

The example is as follows:

Execute the following command to check whether it takes effect.

netsh interface ipv4 show subinterfaces

The output is as follows:

Last updated: 2026.10.14 11:56:02

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