D-Link DIR-645 User Manual page 131

Section 5 - Troubleshooting
What can I do if I forgot my password?
If you forgot your password, you must reset your router. Unfortunately this process will change all your settings back to the factory defaults.
To reset the router, locate the reset button (hole) on the bottom panel of the unit. With the router powered on, use a paperclip to hold the button
down for 10 seconds. Release the button and the router will go through its reboot process. Wait about 30 seconds to access the router. The default
IP address is 192.168.0.1. When logging in, the username is admin and leave the password box empty.
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, and XP 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.
To change the MTU rate on your router follow the steps below:
• Open your browser, enter the IP address of your router (192.168.0.1)
and click OK.
• Enter your username (admin) and password (blank by default). Click
OK to enter the web configuration page for the device.
• Click on Setup and then click Manual Configure.
• To change the MTU enter the number in the MTU field and click Save Settings to save your settings.
• Test your email. If changing the MTU does not resolve the problem, continue changing the MTU in increments of ten.
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