Accessing computer with private IP 1

[sqladmin99]

I set up small network in self storage facility. we have DSL internet connection and wireless router. There are 4 computers connected to wireless router (D-link router), 3 of them are used as digital video recorder (DVR).

We have been paying ISP $60 a month for three public IP addresses. These IP addresses are assigned to 3 computers that have DVR installed on them. I used these public IP addresses to connect to computer so I can monitor video remotely.

Is there anyway I can access these three computers without using separate public addresses? This will be huge saving for me.

I appreciate your help.

RS

 

[lhuegele]

Without getting into specifics, and also because I don't know anything about your DVR software and how it functions over the internet, it should be possible.

Do you connect to the DVR software directly, or are you using something else like Remote Desktop to get into those machines remotely?

LH

 

[kmcferrin]

There are a couple of ways that you can go. You'd definitely want at least one static address. If your wireless router can do PAT as well as NAT, then you set up the router's external address with the static address. Set up your internal PCs with static private IP addresses. Then you make three ports publicly available on that router that redirect to the three private addresses on the correct port.

For example, say you connect to the DVR on port 80 (which is standard http/web traffic). You set each DVR with a static private IP address (192.168.1.10, 192.168.1.11, 192.168.1.12, or something like that) and then make three ports publicly available on the router (say 65000, 65001, and 65002). Then forward the PUBLIC_IP:65000 to 192.168.1.10:80, PUBLIC_IP:65001 to 192.168.1.11:80, PUBLIC_IP:65002 to 192.168.1.12:80.

Of course, if your router doesn't support that (and many of the cheap ones that you get a Best Buy or Circuit City probably don't) then you'll have to try something else. You could either buy a SOHO firewall (Watchguard, Sonicwall, Fortinet, Cisco, etc) that does support PAT, or get something that supports a VPN connection. There's a product called Smoothwall that's free, and you could install it on an old PC. I know that it supports VPN, and probably supports PAT as well.

 

[sqladmin99]

Thanks kmcferrin and lhuegele,

I appreciate your reply. I am going to try what Kmcferrin suggested. I checked the router and it does support PAT.

This is what I am planning to do.

1) I will install dynDNS utility on my computer to avoid buying one IP Address. I will use domain.dynDNS.org to connect to my network.

2) Enable Three port forwarding to local computer.

My only concern is how remote video monitoring software will react to the incoming request from three different port on the router. I will update my post if I succeed in implementing it.

Thanks again.

 

[kmcferrin]

Keep in mind that Port Address Translation is not the same as Port Forwarding. Port Forwarding usually means, "if traffic comes in on port xxx, forward it to the same port (xxx) at IP address yyy.yyy.yyy.yyy." PAT means "if traffic comes in on port xxx, forward it to a different port (zzz) at IP address yyy.yyy.yyy.yyy." So you may still have an issue.

The video monitoring software shouldn't care what the source port is. As long as you're connecting to the port that the software is listening on, it will allow connections. In fact, you can use NETSTAT or Ethereal/Wireshark to monitor all sorts of connections, and you'll see that the source port varies even for well-known connections (i.e., http requests are directed at port 80 on the target system, but they are not sent from port 80).