A good article on modifying the MTU.

The maximum transmission unit (MTU) of a network interface is the size of the largest block of data that can be transmitted as a single unit. Anything larger than the MTU must be broken into smaller units prior to transmission. The following link has a short passage on modifying the MTU.

Change the MTU of a network interface

If you want to change the MTU in the linux kernel source code the macro can be found in

the location

linux/include/uapi/linux/if_ether.h

The macro name is ETH_DATA_LEN and if you are increasing it you need to increase the frame length also. The macro for from length is ETH_FRAME_LEN. I did experiment to modify MTU to 1508. So I modified the ETH_DATA_LEN to 1508 and frame length to 1522.

After the same through ifconfig I was able to set the mtu to 1508.

e.g:- ifconfig eth0 mtu 1508

Setting anything beyond ETH_DATA_LEN the ifconfig will return “SIOCSIFMTU: Invalid argument”. Also changing to any values beyond 1500 ensure your network devices support.

 

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Yogi

17 years of experience in various layers of software. Primarily experienced in system side software design and development on server management software. Interested in linux development in x86 and arm architecture.