In this Post I will show you How to Set DF bit on a Windows Machine (Windows 7).
Below is the PING options output:
H:\>ping
Usage: ping [-t] [-a] [-n count] [-l size] [-f] [-i TTL] [-v TOS]
[-r count] [-s count] [[-j host-list] | [-k host-list]]
[-w timeout] [-R] [-S srcaddr] [-4] [-6] target_name
Options:
-t Ping the specified host until stopped.
To see statistics and continue - type Control-Break;
To stop - type Control-C.
-a Resolve addresses to hostnames.
-n count Number of echo requests to send.
-l size Send buffer size.
-f Set Don't Fragment flag in packet (IPv4-only).
-i TTL Time To Live.
-v TOS Type Of Service (IPv4-only. This setting has been deprecated
and has no effect on the type of service field in the IP Head
er).
-r count Record route for count hops (IPv4-only).
-s count Timestamp for count hops (IPv4-only).
-j host-list Loose source route along host-list (IPv4-only).
-k host-list Strict source route along host-list (IPv4-only).
-w timeout Timeout in milliseconds to wait for each reply.
-R Use routing header to test reverse route also (IPv6-only).
-S srcaddr Source address to use.
-4 Force using IPv4.
-6 Force using IPv6.
Now let's do a Ping test to Yahoo with MTU Size 1470 with DF Bit set.
H:\>ping yahoo.com -f -l 1470
Pinging yahoo.com [98.138.253.109] with 1470 bytes of data:
Reply from 98.138.253.109: bytes=1470 time=352ms TTL=39
Reply from 98.138.253.109: bytes=1470 time=442ms TTL=39
Ok, that's working so now let's do another test with 1500.
H:\>ping yahoo.com -f -l 1500
Pinging yahoo.com [98.138.253.109] with 1500 bytes of data:
Reply from 135.75.222.106: Packet needs to be fragmented but DF set.
Reply from 135.75.222.106: Packet needs to be fragmented but DF set.
Reply from 135.75.222.106: Packet needs to be fragmented but DF set.
Reply from 135.75.222.106: Packet needs to be fragmented but DF set.
HTH...
Sam