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D-Link DSL-245GE User Manual
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 encrypted sites such as banking sites and web mail,
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
.
or
• Click on
Start
and type
cmd
in the
Search
box.
• Once Command Prompt opens, you’ll need type the ping command with parameters. 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.
