Gateway Settings
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The maximum transmission unit (MTU) is the largest data packet a network device transmits. When
one network device communicates across the Internet with another, the data packets travel through
many devices along the way. If a device in the data path has a lower MTU setting than the other
devices, the data packets must be split or “fragmented” to accommodate the device with the smallest
MTU.
The best MTU setting for your gateway is often the default value. In some situations, changing the
value fixes one problem but causes another. Leave the MTU unchanged unless one of these
situations occurs:
You have problems connecting to your ISP or other Internet service, and the technical support of
either the ISP recommends changing the MTU setting. These Web-based applications might require
an MTU change:
n
A secure website that does not open, or only part of a Web page displays
n
Yahoo! Mail
n
MSN portal
n
America Online’s DSL service
n
You use VPN and have severe performance problems.
n
You used a program to optimize MTU for performance reasons, and now you have connectivity
or performance problems.
n
An incorrect MTU setting can cause Internet communication problems. For example, you might
not be able to access certain websites, frames within websites, secure login pages, or FTP or
POP servers.
If you suspect an MTU problem, a common solution is to change the MTU to 1400. If you are willing
to experiment, you can gradually reduce the MTU from the maximum value of 1500 until the problem
goes away. The following table describes common MTU sizes and applications.
The following table lists common MTU sizes.
MTU Size
Application
1500
The largest Ethernet packet size. This setting is typical for connections that do not
use PPPoE or VPN, and is the default value for NETGEAR gateways, adapters,
and switches
1492
Used in PPPoE environments
1472
Maximum size to use for pinging. (Larger packets are fragmented.)
1468
Used in some DHCP environments.
1460
Usable by AOL if you do not have large email attachments, for example.
1436
Used in PPTP environments or with VPN.
1400
Maximum size for AOL DSL.
576
Typical value to connect to dial-up ISPs.
