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Gateway Settings 

79 

 

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: 

● 

A secure website that does not open, or only part of a web page displays 

● 

Yahoo! Mail 

● 

MSN portal 

● 

America Online’s DSL service 

● 

You use VPN and have severe performance problems. 

● 

You used a program to optimize MTU for performance reasons, and now you have 
connectivity or performance problems. 

● 

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. 

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 

Used in PPPoE environments 
 

Maximum size to use for pinging. (Larger packets are fragmented.) 

Used in some DHCP environments. 

Usable by AOL if you do not have large email attachments, for example. 

Used in PPTP environments or with VPN. 

1400  Maximum size for AOL DSL.