How to Calculate MTU Size

MTU (Maximum Transfer Unit)
   Network             MTU (bytes)
   -------------------------------
   16 Mbps Token Ring        17914
   4 Mbps Token Ring          4464
   FDDI                       4352
   Ethernet                   1500
   IEEE 802.3/802.2           1492
   PPPoE (WAN Miniport)       1480
   X.25                        576

Proper Valu 1404

How do I find the proper MTU size on my router?

To find the proper MTU Size, you'll have to do a special ping ofthe destination you're trying to go to. A destination could beanother computer, or a URL.

Step 1 Click on Start and thenclick Run.

Step 2 Windows 95, 98, and ME users type incommand (Windows NT, 2000, and XP users type incmd) and press Enter (or clickOK).

Step 3 Once the window opens, you'll need to do aspecial ping. Use the following syntax:

ping [url] [-f] [-l] [MTU value]

Example: ping yahoo.com -f -l 1472
Example: ping www.tp-link.com -f -l 1472
ping www.dslreports.com -f -l xxxx
ping www.google.com -f -l xxxx
ping www.dslreports.com -f -l 1472

in Ubuntu
Sudo ping yahoo.com -f -l 1472

Drop the test packet size down (10 or 12 bytes) and test again. Notice that the packet still needs to be fragmented

Drop the test packet size down more and test again until your reach a packet size that does not fragment

Once you have a test packet that is not fragmented increase your packet size in small increments and retest until you find the largest possible packet that doesn´t fragment. 

Take the maximum packet size from the ping test and add 28. You add 28 bytes because 20 bytes are reserved for the IP header and 8 bytes must be allocated for the ICMP Echo Request header. Remember: You must add 28 to your results from the ping test!

An example:
1440 Max packet size from Ping Test
+ 28 IP and ICMP headers
1440+28=1468
1468 is your optimum MTU Setting
SHARE

Ibrar Ansari

  • Image
  • Image
  • Image
  • Image
  • Image
    Blogger Comment
    Facebook Comment

0 comments:

Post a Comment