macOS

System Preferences -> Network -> advanced -> Hardware

linux(CentOS)

修改 network-scripts 下面的配置文件后重启网络即可即可， eg: /etc/sysconfig/network-scripts/ifcfg-eth0
查看：
很简单， ifconfig 即可
修改：

MTU="1300"
IPV6_MTU="1300" #If you need

windows

查询:

netsh interface ipv4 show subinterfaces

设置: ( 本地连接等需要双引号)

netsh interface ipv4 set subinterface "本地连接" mtu=1300 store=persistent

参考

windows下修改MTU
linux下修改MTU
理解MTU
The basics – MTU, MSS, GRE, and PMTU (好文，待进一步好好看)