increasing the ethernet MTU greater than 1500 (1502)

John-Mark Gurney gurney_j at
Fri Jan 6 10:02:17 PST 2006

kamal kc wrote this message on Thu, Jan 05, 2006 at 23:18 -0800:
> i tried 
> -->ifconfig xl1 mtu 1502
> but it gave the message:
> -->ifconfig: ioctl (set mtu): invalid argument
> How can i increase the MTU ??? 
> Will it have any effect whatsoever ???
> i guess ethernet should support MTU of 1502. isn't it
> correct ??

Nope, for pre-gige, only 1500 MTU is supported...  This was extended
slightly to support vlan tagging, but I believe many of the drivers to
magic behind the scenes to know when the vlan tagged packets are comming,
and let them through...  You could look at the drivers into fixing this..
If you have a good gige card, you can go to 9000 MTU and beyond...

there is still the problem of the receiving station.. (and all switches,
routers inbetween)...   They must be able to support the larger MTU
packet, otherwise, it coulde get dropped from the wire as too long of
a packet...

  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."

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