On Tue, Oct 09, 2007 at 02:23:41PM +0100, Alex Zeffertt wrote: > Some ethernet drivers implement a change_mtu() method, and use the > MTU size passed in (from ifconfig <dev> mtu <size>) to set the > maximum rx frame size. MTU isn't used for rx. T for transmit. > If a driver is not vlan aware it may set a fixed maximum rx frame > size of 1518, or - if it implements change_mtu() - a maximum rx > frame size of mtu + 18. > > If a driver *is* vlan aware it will add 4 to the above, as it knows > that the frames may have an extra 4 byte shim that gets stripped by > the vlan layer before the frame enters the IP stack. > > For a driver to be q-in-q aware it will need to add 4*(max q-in-q > levels). The driver usually doesn't have too much to say in this. The hardware typically only supports a few maximum packet sizes and >1518 requires varying efforts from one chip to another. //Peter _______________________________________________ Vlan mailing list Vlan@xxxxxxxxxxxxxxx http://www.candelatech.com/mailman/listinfo/vlan
