How do I change the MTU setting for early versions of OS X?
This is for specific older versions of OS X (10.1.1-10.2.1), and fixes the issue discussed in 3.3 above. A better solution for many users is to upgrade to Mac OS 10.2.8 or later. To make the MTU setting permanent: Log in using your administrator account. Start Terminal and enter the following command: sudo pico /etc/ppp/ip-up This will create the file /etc/ppp/ip-up. You now need to type the following into this file: #!/bin/sh /sbin/ifconfig ppp0 mtu 1492 Save the file and exit pico. Next you need to make the file executable. Do this by typing the following command: sudo chmod 755 /etc/ppp/ip-up Now activate your PPPoE connection (reboot and start your internet connection) and run ifconfig ppp0 from a terminal to check your mtu size. It should be set to 1492. If you are interested in why this works, it is described in the pppd man page. (Essentially the pppd process will execute a file called /etc/ppp/ip-up every time you make a ppp/pppoe connection. You just need to tell it what to do
