I am using a Linux as a router.
The machine has two NICs. This router will be used for experiments, so I have set one of it's interfaces to have a MTU that is lower than the standard (let's decide the MTU has been set to 200, for the sake of argument).
Now, most routers (or maybe all routers?) have the ability to decide if they fragments ip packets that exceed the MTU or not.
I would like to have the same behavior on my linux machine - I don't want packets to be fragmented. Oversized packets should be dropped. If the DF flag is on, I would like the interface to return an ICMP messgae ("packet to big. DF set to 1")
How can this be done?