Many users complain that some websites do not open, and usual suggestion is to change the MTU values in modem.
Applications are also recommended for trying different values.
Now the following is another method for MTU selection.
General instruction for finding your optimal MTU size
Go to Start and select Run.
Set router to MTU 1500 to start with.
Type in cmd (Windows 2000/XP/Vista/7) or command (Windows 98/ME) into the box .
Hit the enter key or click OK
At the DOS prompt,
type in ping orreryhim.com -f -l 1492
and hit the Enter key.
If you get the response "Packet needs to be fragmented but DF set",
lower the size the packet in increments of +/-10 (e.g. 1472, 1462, 1440, 1400) until you have a packet size that does not fragment.
Now increase the packet size from this number in small increments until you find the largest size that does not fragment.
Add 28 to that number (IP/ICMP headers) to get the optimal MTU setting.
For example, if the largest packet size from ping tests is 1462, add 28 to 1462 to get a total of 1490 which is the
optimal MTU setting and can be put in your router's settings !
Hope this helps some of you!?
Also you have to change MTU Setting for Windows (for Windows 7 Steps are As)
Are you an admin user when you run the command that is failing?
You also might try this...
1. Open a command line window as an Administrator (ie. right click on All Programs > Accessories > Command Prompt and select Run as administrator) ...
2. Type the command netsh and wait for prompt
3. Type the command interface and wait for prompt
4. Type the command ipv4 and wait for prompt
5. Type the command set subinterface "Local Area Connection" mtu=xxxx store=persistent
Note: It worked for me im BSNL Braodband User on Belkin ADSL Router