the MTU in your enviroment is being set automatically via the DHCP, in your configuration you have this setting: DEVICE=eth0. BOOTPROTO=dhcp. So the DHCP is actually setting the MTU size. In Ubuntu, you can edit the following file: /etc/dhcp/dhclient.conf. Just BEFORE the request line set this two commands: default interface-mtu 1500;
The maximum transmission unit (MTU) of a layer of a communications protocol is the size (in bytes) of the largest protocol data unit that the layer can pass onwards.1. Changing the MTU size with ifconfig tool. In order to change the MTU size, use ifconfig as follows: ifconfig [Interface] mtu [SIZE] up ifconfig eth0 mtu 1500 up How to test if 9000 MTU/Jumbo Frames are working - Blah If you’ve forgotten to enable jumbo frames/9k MTU on your client device you’re sending the ping from you’ll see:. PING xxx.xxx.xxx.xxx (xxx.xxx.xxx.xxx): 8184 data bytes ping: sendto: Message too long If you have enabled jumbo frames on your client but not the destination (or a switch in between) you’ll see: Enabling path MTU discovery algorithm in a Linux machine!! May 17, 2006 How to set a static IP address on Debian 10 Buster? - OSRadar
Enabling path MTU discovery algorithm in a Linux machine!!
How to test if 9000 MTU/Jumbo Frames are working - Blah
How to Optimize Ubuntu Internet Speed with MTU Settings
Below, a Debian 7/8 interfaces file defines eth0 and eth1. eth1 is the 172 network. eth0 could use DHCP as well. 172.16.100.10 is the IP address to assign to eth1. 172.16.100.1 is the IP address of the router. To install Debian on a machine without an Internet connection, it's possible to use CD images (650 MB each) or DVD images (4.4 GB each). Download the first CD or DVD image file, write it using a CD/DVD recorder (or a USB stick on i386 and amd64 ports), and then reboot from that.