How to Change MTU Manually?

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Zaragosa
Posts: 34
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Joined: Thu May 08, 2014 6:27 pm

How to Change MTU Manually?

Post by Zaragosa »

Currently using latest version, 3.4.5.RBJ3, prior to ADM update I was able to set MTU to any value. The values listed are now hard; 1500, 2000, 3000, 4000, 5000, 6000, 7000, 8000, and 9000.

How do I change the MTU size to a value not listed under Settings->Network->Network Interface-><Configure>? I want to set the MTU to 1492.

Thanks in advance
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father.mande
Posts: 1807
Joined: Sat Sep 12, 2015 2:55 am
Location: La Rochelle (France)

Re: How to Change MTU Manually?

Post by father.mande »

Hi,
Zaragosa wrote:Currently using latest version, 3.4.5.RBJ3, prior to ADM update I was able to set MTU to any value. The values listed are now hard; 1500, 2000, 3000, 4000, 5000, 6000, 7000, 8000, and 9000.
How do I change the MTU size to a value not listed under Settings->Network->Network Interface-><Configure>? I want to set the MTU to 1492.
Thanks in advance
MTU is by definition a maximum, so negotiated by the 2 end points
... so if on point propose 1492 the other 1500 the real used MTU is 1492

MTU have multiple definition due to change in link support
... for ex. 1492 and 1500 are same if one implementation use the definition (as for ADSL) without I.P. headers (8) or with include headers ... so 1500 (I repeat negotiated) is a current proposal to support each case

In all case you can try to set the MTU you want ... if the hardware (Ethernet chip) and the software (network stack) support it by using the command ip
... ip link set or down / set / up (use a script and start it in a screen or tmux to avoid terminal ssh / telnet disconnection)

Take care if something goes wrong ... you can lost network access, so
... test on one Ethernet if you have multiple Ethernet (and configure the second to keep an access)
... or use a short reset to return to basic network and password configuration without loosing data and application.

I suppose a script exist somewhere in /usr/builtin/etc ... but I have no time to search it ...

Philippe.
AS6602T / AS5202T /AS5002T / AS1002T / FS6706T
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