I am studying the manual of the telnet command, and I have some difficulty in understanding the following:

2.20.4 wan DF_check
This command allows you to enable or disable the function of DF (Don’t fragment)
wan DF_check [on]
wan DF_check [off]
Syntax Description
on/off It means to enable or disable DF.

This description is very poor.
What does it mean ?
I know the packet fragmentation and the don't fragment bit in TCP/IP, but I don't understand what is the 'DF function' in Vigor device.
In particular, if my Vigor2700 is configured with

> wan DF_check ?
%DF bit check is Disable!

What does it mean ?
Perhaps it means that the DF bit will be ignored and if necessary the packet will be fragmented anyway ?

Thanks,

I cant remeber which way round it is, but you can test it using a ping -l <size> where <size> is too big. It'll either fragment and send the packets or it will error.

I sent the question to technical support.
The response was: if DF_check is disabled (default) the router doesn't check "don't fragment bit", and if needed the packets are fragmented anyway.