3Com 3CRWDR101B-75, 3CRWDR101A-75 manual Configuring the Router

84CHAPTER 5: CONFIGURING THE ROUTER

you turn NAT off, the computers on your network will not be able to access the Internet. Other problems may also occur.

■IPSEC NAT-T Pass-through — NAT-T (NAT Traversal) is an Internet Draft proposed to IETF in order to help the problems associated with passing IPsec traffic through NAT Routers. For NAT-T to work, both ends of the connection need to support this function. Ensure that you select NAT-T only if it is needed as it will reduce LAN-WAN throughput. This Router supports NAT-T draft 2 implementation.

■Universal Plug and Play — This is a technology that offers seamless operation of voice messaging, video messaging, games, and other applications that are Universal Plug and Play compliant. Some applications require the Router's firewall to be configured in a specific way to operate properly. This usually requires opening TCP and UDP ports and in some instances setting trigger ports. An application that is Universal Plug and Play compliant has the ability to communicate with the Router, basically "telling" the Router which way it needs the firewall configured. The Router ships with the Universal Plug and Play feature disabled. If you are using any applications that are Universal Plug and Play compliant, and want to take advantage of the Universal Plug and Play features, you can enable this feature. Simply check the Enable Universal Plug and Play checkbox. Click Apply to save the change.

■WAN Ping Blocking — Computer hackers use what is known as "Pinging" to find potential victims on the Internet. By pinging a specific IP address and receiving a response from the IP address, a hacker can determine that something of interest might be there. The Router can be set up so it will not respond to an Internet Control Message Protocol (ICMP) Ping from the outside. This heightens the level of security of your Router. To turn off the ping response, check Block ICMP Ping and click Apply; the Router will not respond to an ICMP ping from the Internet.

■MSS Clamping — You might not be able to browse some Web sites or to send email messages that contain attachments from an Internet Connection Sharing client computer if your outbound connection is through a Windows XP-based Internet Connection Sharing host computer that uses Point-to-Point Protocol over Ethernet (PPPoE). This issue may occur if the Windows XP-based Internet Connection Sharing host computer uses a smaller Maximum Transmission Unit (MTU) size on the WAN interface (the PPPoE connection to the Internet) than it uses on the private interface (the Ethernet connection to the Internet Connection Sharing client). If a packet is larger than