Linksys cable/DSL Router Help

NOTE: Even though a game is listed as "supported" by the Linksys, you still might not be able to get it to work for you. See the Gaming Help section for an explanation.

Tip: If you are using newer Linksys firmware that supports port range forwarding and want to map a single port, enter the same port number in both port number boxes.

Tip: Reader Jamie Tyson says that enabling the MTU function on the Filters page helped the packet-drop problems he was having with FTP serving and WinVNC. He says it helped fix some gaming problems he was having, too. Start with an MTU value of 1000 or so and experiment.

In general, assume that you will not be able to use the Linksys to allow multiple users to access on-line games, Internet communication applications like Dialpad or Netmeeting, or any application that uses port ranges or dynamically assigned ports. The best you'll be able to do is to allow access from one computer connected to the LAN side of the router. There are exceptions to this rule of thumb, but I'd rather set your expectations lower, rather than higher.

The following popular applications work from Client computers without using the Port Forwarding or DMZ Computer features (I guess this is the "Application Sensing Tunnel" at work!):

Note that we continue to receive reports of players getting kicked off Quake2 and 3 servers that are behind the Linksys. No solution has been found for this problem.

There's a Quake3world.com Forum that's discussing this subject, so check it out, too.

How to set up Quake III for multiple users behind a NAT firewall (Thanks to Russell Haupert!)

Typically, many Quake III users have been reporting that Quake III is unable to support multiple player connections from behind a NAT. While the first player behind the NAT joins fine, adding additional players is problematic in the default configuration. Symptoms include rejected challenges, dropped delta packets, and severe "connection interrupted" messages.

By default, Quake III clients send and receive data over the same port, causing the server to treat multiple clients as a single data connection. Quake III does have the ability to specify individual client ports for communication by adding a command line switch. Follow the procedure below to add this switch.

1. Right click on the QIII icon

2. Choose "Properties"

3. In the Target field you'll see a line like "C:\Program Files\Quake III Arena\quake3.exe"

4. Add the Quake III net_port command to specify a unique communication port for each system. The complete field should look like this: "C:\Program Files\Quake III Arena\quake3.exe" +set net_port 27660

5. Click OK.

6. Repeat for each system behind the NAT, adding one to the net_port selected (27660,27661,27662)

The following games will work, but require port forwarding. If you don't know which ports to use, check this page, the Support section of your game's Web site, or your game's Help files.

The following games require mapped port ranges and you must have firmware 1.33 or higher and forward the appropriate ranges.
(You can find port information on this page. See also this Microsoft KB article).

The following popular applications work from Client computers but require the computer to be set as the DMZ computer:

If you are using 1.30.5 or higher firmware and still having problems with loopback, try making a HOSTS file entry for the address of the server that you're having problems with. You should also be using a static IP address for any port forwarded machines. If you use DHCP for any port forwarded machines, they could lease a different IP when they renew their lease and break your forwarding.

(Broken in all other revs since V1.22)
(The following information is for reference only.)

If you have Web, FTP, or other servers on your LAN that you have mapped or forwarded so that they are accessible from the Internet, you would expect to be able to get to them by using the IP address assigned to you by your ISP. If you use a dynamic IP service, you'd also probably expect to be able to access the server by your domain name.

Unfortunately, the router doesn't presently support this capability, sometimes referred to as "loopback". You'll need to use the private IP address, i.e. 192.168.1.X of the desired server when you are trying to use it from a computer on your LAN. The ISP-assigned address will work only from computers connecting from the Internet.

Problem: You're using Dyndns' service and it's not detecting when your ISP assigns you a new IP address. This is because the router is receiving the new IP from your ISP and the client software that is supposed to detect the changing IP address can't see it change.

Bobby Griggs has authored a client that extracts the IP info from the LinkSys router and updates a user's DynDNS record. The client is very simple, written in Python and free. Go here to download it.

Helpful reader Chris Holt also points out that you can use the DynSite program found on DYNDNS' site.

TZO's Beta client will support any hardware router and properly update TZO's DNS servers when your WAN IP address changes. You can also control how often you are polled for your IP address.

- You MUST shutdown the TZO software before installing the new version. - Send comments to BETATEST@TZO.COM

The IP Poster will automatically check the IP address that your ISP's DHCP server has assigned to your Linksys Router and post the results to the site of your choice using FTP. It runs on Win95/98/NT/2000.

You can download the program from here (IP_Poster_For_LinkSys.exe 248KB). You can also download the source code, too!

You can also use TZO's MyWanIP, which will work with any Internet connected device!

2) Setting up mIRC DCC
(Thanks to Patrick Fortin-Ducharme for providing this info!)

The logging mechanism added in V1.35 is performed via a standard SNMP Trap message that is sent to the configured machine on UDP port 162. If you're not happy with the Windows logviewer.exe application that you can get from Linksys (see this page), you can use any SNMP Trap application to view and archive logs. Go here for a list. Also see the Tools page for alternative logging applications, written specifically for Linky.

Linksys has made a newer version of logviewer.exe available on their FTP site [Filename: logviewer.exe 1.26Mb Windows executable]. Doesn't come with any documentation or help, but you just run the .exe file to install, then enter the IP address of the LAN client that is running logviewer into the box on the LOG tab of the router admin screens. The new version lets you Empty (clear) and Save logs as well as display them.

[Editor's Note:] I had an install error involving the msvcrt.dll file on one of my machines (Win98SE). Could be due to having an older/newer version of the file in C:\windows\system. Reader Pete Jacoby got around this by booting into Safe Mode (without network support) and installing logviewer.

The SPI feature is located on the Filters page of some BETA versions of Linksys firmware (1.38.5 for example). The information below was supplied by Linksys:

The SPI (Stateful Packet Inspection) option is currently an experimental feature. If you enable this feature, it will DISABLE THE FORWARDING FEATURES. The reason forwarding is disabled is to test the SPI and make sure forwarding is not a factor. In the released version, forwarding will not be disabled when SPI is enabled.

The SPI feature can be tested by using applications like Netmeeting and other applications that use many ports dynamically. SPI will open the ports as needed as long as the data transfer session originates from a LAN side computer. When the initial data transfer comes from the WAN side of the router, the normal port Forwarding feature must be used (however, remember that Forwarding is disabled in the BETA).

The Triggered Port button on the Forwarding page brings up a screen where you enter a trigger port range and incoming port range for up to 10 applications. This is basically a manual version of SPI. The trigger port ranges are monitored and the incoming port range enabled when a data transfer using those ports is detected from a LAN client. The ports are opened only for the transfer, then closed again.

If you can't connect to your PCAnywhere machine behind the Linksys, even trying DMZ, the problem may be your firmware. Here is an article from Symantec's Knowledge Base that describes the problem:

Notes:
- Using older firmware or other routers that don't pass UDP ports. The new Citrix Win32 client has a network protocol option of TCP/IP + HTTP which works for routers that do not pass UDP packets, provided that the server has been configured for this. This is also an option with the Linksys if you want to disable Multicast PassThrough.

- TCP 1494 is a registered port for ICA. Some ISPs may filter this port for residential service. You can test this by using Telnet to contact the host (Citrix Server) using port 1494. You should receive a sounder that consists of two block characters and the letters ICA repeating.

- If the Citrix Server is hosted on an NT Server, the following applies: The NT TCP port allocation algorithm is to index the ports used from the minimum user port (1025) upwards. A counter is maintained of the last one allocated, and is incremented for each allocation. A check is then made to make sure no other connection is using this port, and if so, the algorithm iterates until it finds a free port. The NT TCP/IP ports are a function of how many other connections have been made, and are not random. The maximum user port used by default is 5000, but a registry key "Max UserPort" can set this up to the TCP/IP maximum of 65534.