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How do I override an MTU provided by DHCP?

rated 0 times [ 6] [ 0] / answers: 1 / hits: 14368 / 3 Years ago, mon, august 23, 2021, 4:18:24

I'm running Ubuntu Server 12.04 LTS, and I want to override the MTU my cable company provides via DHCP. They provide an MTU of 576 and I want to use 1492. I can change it with ifconfig, but it won't persist across reboots. I tried to edit the file /etc/network/interfaces, but the setting gets ignored on the interface (the MTU setting works on the internal interface that uses a static IP address). How can I make the interface force an MTU of 1492 even when it is provided with an MTU via DHCP?

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tusmuumu

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1 Year ago

answered 3 Years ago shadowoof · Accepted Answer

Edit the interfaces file to set the mtu when the interface comes up:

$ sudo vi /etc/network/interfaces

Edit the file so it includes the post-up line:

iface eth0 inet dhcp

    . . .

    post-up /sbin/ifconfig eth0 mtu 1500