D-Link AC750 User Manual page 126

Section 7 - Troubleshooting
3..Why.can't.I.connect.to.certain.sites.or.send.and.receive.emails.when.connecting.through.my.router?
.
If you are having a problem sending or receiving email, 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).
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, Vista®, and 7 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.[url].[-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.
D-Link DIR-510L User Manual 122