Script Cream

Maximise your transmissions.

Download Set MTU 0.2

Sometimes you have to change the Maximum Transmission Unit on a network interface in Mac OS X to fix or debug a connection problem.  You can dive into the command line using ifconfig:

ifconfig en0 mtu 1458

Or you can change it in the advanced settings of the Ethernet interface, but for other interfaces you have to use ifconfig.  Well, not anymore.  Using this script you can easily set one or more interfaces to a new MTU value (on both Tiger (10.4) and Leopard (10.5), and possibly on older versions of Mac OS X).  Due to the differences in systems older than Leopard however, the script can’t lookup the friendly interface name (”Built-in Ethernet”, “Airport”, “Firewire” and so on) but lists the interface UNIX name (en0, en1, fw0 etc). It does make a wild guess at which interface it is though based on the usual assignments.

Tested on:

  • Mac OS X 10.4 (Tiger)
  • Mac OS X 10.5 (Leopard)

Licensed under the GPL. Download the Set MTU 0.2 script application (zip).


  • 0.2
    • Added function to calculate maximum MTU, taken in part from mtutest_sh by Ben Goren.
  • 0.1
    • Initial release.
  1. Arno
    December 1, 2008 at 8:18 pm

    the link to the SET MTU is not working !

  2. December 2, 2008 at 12:07 pm

    Unfortunately my website provider moved to a new platform and deleted all my content, so I am trying to patch it together from a few backups, which is why the download links don’t work. You can set the MTU from the Ethernet tab of the Advanced settings of the Ethernet adaptor in Tiger and Leopard, and you can do the same for Airport, although that’s Leopard only.

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