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Remote Site Access and Connectivity via Wireline
After the configurations are done, you'll tell the client software to open the VPN tunnel. Once you have it working, you'll then connect to hosts on the far end by referring to them with their remote network addresses. Say for example my Nautel VS2.5 was given an address on the remote LAN of 192.168.1.100. When I open a browser on my client machine, I would use that address.
There is another approach to the same problem of having multiple hosts on the private side of a DSL or cable modem, and that's by using port translation. (Thanks to Dennis Sloatman of CCLA for showing me this one.) In this example we'll look at a simple D-Link EBR 2310, using its feature called "virtual server."
First though let's review the problem at hand. Say you have a remote Internet connection with a cable or DSL modem (with router functions). Your ISP has given you one IP address. You, of course, have more than one device to install on the private side of that router; and, to make matter worse, each of those devices expects to see requests coming in for port 80. You can use the VPN approach that I described already, or you can use port translation, to be described below.
After the device is attached to its Internet connection, you of course have a little bit of configuring to take care of. You'll select the "advanced" tab next. See Figure 6. This shows a typical configuration for "virtual server" on this D-Link. Here are the instructions previously given to this router:
The KVVS Wi-fi modem is accessed remotely by sending messages to the public IP, requesting port 9066. When the router receives these packets, they translated for the private side, and sent to the host at address 192.168.252.50, port 80.
The KVVS webcam is accessed remotely by sending messages to the public IP, requesting port 1024. When the router receives these packets, they're translated for the private side, sent to the host at address 192.168.252.40, port 80 (again).
There is a Barix Exstreamer that can be accessed remotely by sending messages to the public IP, requesting port 9152. The D-link recognizes these packets, and translates them for the private side, sending them to the host at address 192.168.252.60, using port 80 yet again.
You can go on and on with this, adding practically as many hosts as you want. The limit likely has more to do with the link's connection speed than anything else. I should note that the port numbers configured for the public side are random.
Often times I feel like I need to be in more than one place at the same time. Clearly I can only stand in front of one rack at a time; but with reliable, fast remote access, I can virtually be in many places at the same time. It makes my job easier, as it will yours. Knowing what is going on at all those remote sites -- or at least being able to figure it out fast, does give me some peace of mind, and some satisfaction in that I feel everything is under control.
Irwin is RF engineer/project manager for Clear Channel Los Angeles. Contact him at firstname.lastname@example.org.
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