Monday, May 21, 2012

Configuring Jumbo MTU in Windows or Linux

If you are in to networking area, you might know that jumbo frames are Ethernet frames with more than 1500 bytes of payload, and if you ever try to capture these packets with a standard configured operating system you will see that these packets would not seem to come to your NIC card. this is because the OS are not configured for Jumbo MTU's. If your NIC supports jumbo frames,  you can configure your OS as explained below:

 Microsoft Windows

  1. In Microsoft Windows, right-click the Network Adapter in Network Connections, and then click Properties.
  2. Click the Configure button and then the General tab. Jumbo MTU is set at 1500 bytes by default (disabled). To increase the size of the received frames, select a value that is available by NIC driver.

Linux (Debian/Ubuntu)


The MTU of an interface can be changed temporarily using the mtu option of the ifconfig command:

ifconfig eth0 mtu 9000

The new MTU will not persist beyond a reboot.


If the interface has (or can be given) a static configuration in /etc/network/interfaces then its MTU can be persistently altered by adding an mtu option to the relevant iface stanza, for example:

auto eth0
iface eth0 inet static
 mtu 9000

This method does not work when using other configuration methods such as dhcp.

You can activate the new MTU can by taking the interface down using ifdown then bringing it back up using ifup:
ifdown eth0
ifup eth0
Alternatively you could reboot the machine.


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