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Why can't I change the MTU for a value lower than 1280?

Since I've couldn't open linkedin page (www.linkedin.com) I've tried to lower the MTU value to 1000. but I can't change it to less than 1280. How can I change it or is there any other way to do it? I'm running a Mountain Lion 10.8.2 in a Macbook Pro.

MacBook Pro, OS X Mountain Lion (10.8.2)

Posted on Feb 24, 2013 11:54 PM

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1 reply

Feb 25, 2013 12:20 AM in response to tiago.feldberg

Hi, 2 ways...


Sys Prefs>Network, highlight the Interface you use for Internet, Adavanced>Hardware tab>Configure Manulaly>MTU.


You can temporarily test by pasting this into Terminal, (will go back to defaults when you reboot)...


sudo ifconfig en1 mtu 1000


Or en0 for ethernet & whatever value you want.


Different Servers/Routers/Modems may have different MTUs, and that can cause Havoc, here's some guides on that issue...


Setting MTU size is a process of trial-and-error: start with the maximum value of 1500, then reduce the size until the problem goes away. Using one of these values is likely to solve problems caused by MTU size:

• 1500. The largest Ethernet packet size; it is also the default value. This is the typical setting for non-PPPoE, non-VPN connections. The default value for NETGEAR routers, adapters and switches.

• 1492. The size PPPoE prefers.

• 1472. Maximum size to use for pinging. (Bigger packets are fragmented.)

• 1468. The size DHCP prefers.

• 1460. Usable by AOL if you don't have large email attachments, etc.

• 1430. The size VPN and PPTP prefer.

• 1400. Maximum size for AOL DSL.

• 576. Typical value to connect to dial-up ISPs

Why can't I change the MTU for a value lower than 1280?

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