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Author Topic: Checking MTU router/modem values  (Read 38689 times)


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    • Router Troubleshooting
Checking MTU router/modem values
« on: March 11, 2013, 09:13:18 AM »

Why can’t I connect to certain sites or send and receive e-mails when connecting through my router?

If you are having a problem sending or receiving e-mail, or connecting to secure sites such as eBay, banking sites, and Hotmail, we suggest lowering
the MTU in increments of ten (Ex. 1492, 1482, 1472, etc).
Note: AOL DSL+ users must use MTU of 1400. Most Cable ISP users should use 1500. Contact your ISP service support to ask what is officially used and supported for there services.

To find the proper MTU Size, you’ll have to do a special ping of the destination you’re trying to go to. A destination could be another computer, or a URL.
• Click on Start and then click Run.
• Windows® 95, 98, and Me users type in command (Windows® NT, 2000, XP, and Windows 8 users type in cmd) and press Enter (or click OK).
• Once the window opens, you’ll need to do a special ping. Use the following syntax:
ping [-f] [-l] [MTU value]
Example: ping yahoo.com -f -l 1472

You should start at 1472 and work your way down by 10 each time. Once you get a reply, go up by 2 until you get a fragmented packet. Take that value and add 28 to the value to account for the various TCP/IP headers. For example, lets say that 1452 was the proper value, the actual MTU size would be 1480, which is the optimum for the network we’re working with (1452+28=1480).

Once you find your MTU, you can now configure your router with the proper MTU size.

Additional Resources:
Linksys Recommended MTU Value for Xbox 360

« Last Edit: November 14, 2016, 11:37:34 AM by FurryNutz »
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