D-Link DVA-2800 User Manual page 95

Section 6 - Troubleshooting
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 (192.168.1.1) and click OK.
• Enter your username (admin) and password (sometimes 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.
D-Link DVA-2800 User Manual 91