Scanner:<br>
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ALL valid IP addresses on the Internet are registered with one of several (is it three, I think?) organizations. For the Americas (N & S) and part of Africa, this organization is ARIN (American Registry for Internet Numbers). When speaking of the Class A,B,& C IP ranges that are reserved (orginally for testing purposes, I believe), these are IP addresses that are never valid on the Internet. They are filtered (usually immediately) at the ISP or upstream routers.<br>
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Blocks of IP Addresses are handed out to service providers by ARIN. The service providers each form their own AS (Autonomous Systems) that communicate with other AS's (think of them as blocks of IPs of a service provider). Your company exists as a client of a particular service provider. They grant you a subset of IPs from their assigned block to use as valid IP addresses on the Internet. This subset of addresses is still owned by the service provider, you are just leasing them. Often, this subset is very small and your company will far more devices, than IPs that you'd like to communicate to the Internet. This is where Proxies and Native Address Translation come in. You use a private or arbritrary (sp?) address scheme within your company that goes thru a Proxy or NAT device. The proxy or NAT device presents a valid IP address when forwarding traffic to the Internet.<br>
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Now hopefully I've answered your questions somewhat by my diatribe. But I'll address the RoadRunner...<br>
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Cable Modems are Layer 2 devices (for the most part, I'm more familiar with LanCity modems). Generally, they'll be set to recognize the first MAC address or a single MAC/IP pair on the wire and ignore the rest. So, changing a NIC or trying to put multiple devices off the modem doesn't work. You can either get a proxy (such as IIS or Netscape Proxies) or a NAT-capable hub-router (Cayman or Flowpoint/Cabletron come to mind) or something inbetween (like the IP-Fliter software). These will present a single IP address/MAC address to the cable modem and you can use whatever IP scheme your heart desires behind it.<br>
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I hope that helps...<br>
jfk<br>