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Changing the MTU

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 any 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 one with the smallest MTU.

The best MTU setting for NETGEAR equipment is often just the default value, and changing the value might fix one problem but cause another. Leave MTU unchanged unless one of these situations occurs:

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. Table 5-1. describes common MTU sizes and applications.

Table 5-1. Common MTU Sizes
The largest Ethernet packet size and the default value. This is the typical setting for non-PPPoE, non-VPN connections, and is the default value for NETGEAR routers, 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 don't have large e-mail attachments, for example.
Used in PPTP environments or with VPN.
Maximum size for AOL DSL.
Typical value to connect to dial-up ISPs.

To change the MTU size:

  1. In the main menu, under Advanced, select WAN Setup.
  2. In the MTU Size field, enter a new size between 64 and 1500.
  3. Click Apply to save the new configuration.

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