figure 9-1: wan setup menu
the wan setup options let you configure a dmz server, change the mtu size and set the wan port speed. these options are discussed below.
1 connect automatically, as required
normally, this option should be enabled, so that an internet connection will be made automatically, whenever internet-bound traffic is detected. in locations where internet access is billed by the minute, if this causes high connection costs, you can disable this setting.
if disabled, you must connect manually, using the sub-screen accessed from the router status menu "show wan status" screen.
2 setting up a 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 can be used to attack your network.
the use of the term ‘dmz’ has become common, although it is a misnomer. in traditional firewalls, a dmz is actually a separate physical network port. a true dmz port is for connecting servers that require greater access from the outside, and will therefore be provided with a different level of security by the firewall. a better term for our application is exposed host.
the default dmz server feature is helpful when using some online games and videoconferencing applications that are incompatible with nat. the router is programmed to recognize some of these applications and to work properly with them, but there are other applications that may not function well. in some cases, one local computer can run the application properly if that computer’s ip address is entered as the default dmz server.
incoming traffic from the internet is normally discarded by the router unless the traffic is a response to one of your local computers or a service that you have configured in the ports menu. instead of discarding this traffic, you can have it forwarded to one computer on your network. this computer is called the default dmz server.
the wan setup menu, lets you configure a default dmz server.
to assign a computer or server to be a default dmz server, follow these steps:
1. click wan setup link on the advanced section of the main menu.
2. type the ip address for that server. to remove the default dmz server, replace the ip address numbers with all zeros.
3. click apply.
1 respond to ping on internet wan port
if you want the router to respond to a 'ping' from the internet, click the ‘respond to ping on internet wan port’ check box. this should only be used as a diagnostic tool, since it allows your router to be discovered. do not check this box unless you have a specific reason to do so.
2 setting the mtu size
the default mtu size is usually fine. the normal mtu (maximum transmit unit) value for most ethernet networks is 1500 bytes. for some isps, particularly those using pppoe, you may need to reduce the mtu. this should not be done unless you are sure it is necessary for your isp.
any packets sent through the router that are larger than the configured mtu size will be repackaged into smaller packets to meet the mtu requirement. to change the mtu size, under mtu size, enter a new size between 64 and 1500. then, click apply to save the new configuration.
3 setting the wan port speed
in most cases, your router can automatically determine the connection speed of the internet (wan) port. if you cannot establish an internet connection and the internet led blinks continuously, you may need to manually select the port speed.
if you know that the ethernet port on your broadband modem supports 100baset, select 100m; otherwise, select 10m.