Computers Using DSL and Cable Modems Are Unable To Receive Incoming LapLink and PCsync Connections
- Search Again SUMMARY I have a new Digital Subscriber Line (DSL) to connect to the Internet. I can make outgoing connections to other computers running LapLink, but incoming connections won't work. I've tried using a cable modem with PCsync and have the same problem. Can you help me?
CAUSE The problem happens when the high-speed connection devices (either DSL or cable modem) uses Network Address Translation as part of it's connection to the Internet.
Network Address Translation (NAT) devices work to allow multiple computers to share a single Internet Protocol (IP) address. The IP address acts as an identification tag for a computer when it is connected to the Internet. There are two kinds of IP addresses available, called routable and non-routable. Routable IP addresses can be used on the Internet, however, since there is a limited number of routable addresses available, non-routable addresses are used on Local Area Networks (LAN).
A NAT device takes the non-routable IP addresses in data packets from source computers on the LAN side of it's connection and replaces them with the single routable IP address assigned to the NAT device. It also assigns additional "tag" information that allows the NAT device to keep track of connections made to the Internet. When a target computer replies back to a source computer, the reply data packet will also include that tag information, letting the NAT device route the data packets on to the proper machine. This is how LapLink can make an outgoing connection from a source computer behind a NAT device.
SOLUTION If your computer shares the high-speed connection with other computers on a LAN:
One way to tell if your high-speed device uses NAT is to find out the IP address assigned to the computer running LapLink. The procedure for this is in Technical Document 32, How To Determine If a Computer Is Assigned a Non-routable IP Address. If your computer has been assigned a non-routable IP address, then your high-speed connection is using NAT, and you will not be able to accept any incoming LapLink or PCsync connections.
The exception to this situation is if the high-speed device has a router that uses a router table to map ports. The router must be on the same LAN as the high-speed connection device. In these cases, the router table can have ports used by LapLink or PCsync added. Click here for a list of routers that LapLink may work with. Click here for a list of routers that PCsync may work with.
If the high-speed device is attached to your computer directly:
Your high-speed connection device may also use a router. If so, the router table can have the ports used by LapLink or PCsync added. Click here for a list of routers that LapLink may work with. Click here for a list of routers that PCsync may work with. Consult with your Internet Service Provider for additional assistance in configuring the router.
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