C o n f i g u r a t i o n 4-71A significant advantage of NAT is that you can configure it without changinghosts or routers, other than those few routers on which NAT is configured.NAT multiplexes internal network traffic and presents it to the Internet as if itis from a single source with one IP address.Enable/Disable NAT Translation by PortEach IAD is configured with NAT disabled. To enable NAT translation,follow the steps below.1 Type “P” on the NAT Configuration menu. If at least one virtual circuit onthe WAN exists and the LAN port is also configured with an IP address, ormore than one PVC exists, the IAD displays the interfaces (samplefollowing) on this IAD as shown in Figure 4.9. Otherwise, the IAD displaysthe WAN port table and prompts you to select a port.2 Type the port number on which to enable NAT and press Enter. The IADprompts you to enable or disable NAT.3 Type “E” to enable NAT, or “D” to disable. The IAD saves the setting anddisplays the NAT Configuration menu.4 Continue with other NAT configuration tasks, or press Escape to return tothe Main menu.Configure NAT TCP and UDP TimeoutsUnder normal circumstances, the timeout default setting is adequate.However, if users interact with products including multiple-player IP gamesor video conferencing, you may need to configure the timeout.The local server protocol you select determines which timeout to configure.TDP and UDP are similar, except that TCP tracks TCP clients on a per-connection basis and removes them from the table as soon as the connectioncloses.To configure a NAT timeout, follow the steps below.1 On the NAT Configuration menu, type “T” to select TCP connections, ortype “U” to select UDP connections. The IAD displays a TCP or UPDprompt.2 Type the timeout value and press Enter. The IAD displays the NATConfiguration menu.3 Continue with other NAT configuration tasks, or press Escape to return tothe Main menu (Figure 2.2).4 Reset the IAD.Configure NAT Port RangeThe size of the NAT port range defines the number of simultaneousconnections permitted. A small port range limits the number of connections.Since the range that you assign must be outside the range of assigned ports,do not set port ranges below 5,000.
