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Thread: I have a general question about NAT & T1

  1. #1
    Senior Member br_fusion's Avatar
    Join Date
    Apr 2002

    I have a general question about NAT & T1

    Hey i'm a little confused on how my school network is set up(and no i'm not trying to break into it) Well the computers run on a t1 line. I run a net view and it shows that all of the computers are networked in the whole county. (You can even access their shares) How can these computers share an internet connection that are so far away. (is this a WAN?) I also notice that all of the computers ip's are private(172....) This leads me to believe that the network is running Network Address Translation. I also checked out the gateway(which is in the router) ip address and it is also a private IP?!?!(shouldn't it be outside of the NAT LAN) So to sum things up, how does the router perform all of this? And also we are setting up ftp clients for our webpages we are making. Though you can't ftp to the computers because of the private LAN?!? I guess its impossible to do so.

    Thanks again fellas

  2. #2
    Senior Member
    Join Date
    Aug 2002
    First of all, yes, this would be considered a WAN because of the physical separation, even though they share an internet connection. The thing is this, they are probably leasing some line to connect with the remote LANs. For the router that is connected to the internet, there are at least the two interfaces. The router/firewall probably has one interface per remote LAN, and the other is connected to your ISP. The LAN interfaces have local/private IPs (This would explain why you found a private IP on the Router as it has to be able to communicate on your network to map a route to other destinations - like the internet - in its routing table or on other locally connected networks .). You probably have a few public IPs that map to and from the local/private addies. This makes address assignment more efficient because no matter what machine initiates traffic to the internet, it originates from the one public IP. That means that you have to pay for less IP addresses. It also means a little bit of security since someone from the outside cannot initiate traffic directly to a machine with a private IP addy across the internet. Now if they tapped your network locally, that's a different story. I hope that I didn't confuse you too much. You might want to do a google on NAT for a good explanation or search here on AO. Hope that helps.

    Edit: And about the ftp thing, they would only be able to ftp to the webservers under two conditions (both would need to be met): 1. the webservers are publicly accessible with a public IP addy and 2. an ftp server is running on the machines.

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