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You can select this check box to disable the feature if you do not need it. •MTU Size (in bytes). The normal MTU (maximum transmit unit) value for most Ethernet networks is 1500 bytes, or 1492 bytes for PPPoE connections. For some ISPs, you might need to reduce the MTU. This is rarely required, and should not be done unless you are sure that it is necessary for your ISP connection. See Change the MTU Size on page 35. •NAT Filtering. Network Address Translation (NAT) determines how the router processes inbound traffic. Secured NAT provides a secured firewall to protect the computers on the LAN from attacks from the Internet, but might prevent some Internet games, point-to-point applications, or multimedia applications from functioning. Open NAT provides a much less secured firewall, but allows almost all Internet applications to function. Default DMZ Server The default DMZ server feature is helpful when you are using some online games and videoconferencing applications that are incompatible with Network Address Translation (NAT). The router is programmed to recognize some of these applications and to work correctly with them, but other applications might not function well. In some cases, one local computer can run the application correctly if that computer’s IP address is entered as the default DMZ server. DMZ servers pose a security risk. A computer designated as the default DMZ server loses much of the protection of the firewall and is exposed to exploits from the Internet. If compromised, the DMZ server computer can be used to attack other computers on your network. The router discards incoming traffic from the Internet unless the traffic is a response to one of your local computers or a service that you have configured in the Port Forwarding/Port Triggering screen. Instead of discarding this traffic, you can have the router forward traffic to one computer on your network. This computer is called the default DMZ server. 1.On the WAN Setup screen, select the Default DMZ Server check box. 2.Type the IP address. 3.Click Apply. Change the MTU Size 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 have to be split or “fragmented” to accommodate the device 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: •You have problems connecting to your ISP or other Internet service, and the technical support of either the ISP or NETGEAR recommends changing the MTU setting. These web-based applications might require an MTU change: -A secure website that does not open, or displays only part of a web page -Yahoo email -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. Note:An incorrect MTU setting can cause Internet communication problems such as the inability 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. Table 2. Common MTU sizes MTU Application 1500 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. 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. 1.Select Advanced > Setup > WAN Setup. 2.In the MTU Size field, enter a new size from 64 through 1500. 3.Click Apply to save the settings. The LAN Setup screen allows configuration of LAN IP services such as Dynamic Host Configuration Protocol (DHCP) and Routing Information Protocol (RIP). The router is shipped preconfigured to use private IP addresses on the LAN side and to act as a DHCP server. The router’s default LAN IP configuration is: •LAN IP address. 192.168.1.1 •Subnet mask. 255.255.255.0 These addresses are part of the designated private address range for use in private networks and should be suitable for most applications. If your network requires a different IP addressing scheme, you can change these settings in the LAN Setup screen. Note:If you c...