>> Third, if you live in a house with a single address, you cannot >> publicly start announcing different addresses without the postal >> service knowing about it. If packets should arrive at your home, then >> you better make sure you write your street and number on the >> announcement, other things just won't work. >> > >No but I use the following format: address+office1 ... address+officeN! >That's what I try to achieve with the IPs as well but without having to use >port numbers!
While this analogy is probably starting to get a little stretched, address + officeN is analogous to ip:port. IP address is like a postal service address, it tells where a packet should physically go to. once it gets to that address, its up to the receiving computer to figure out which program is listening to the port the packet arrived on. When you send a letter to address + officeN, the post office doesn't care about the officeN part, it just looks at the address to get the packet there. >> Last but not least: _if_ your ADSL provider will assign and route >> multiple addresses to your router (for example a complete C network), >> then you can - of course - translate the different numbers into >> different numbers in your internal network. But then: why you are not >> using these IPs for your internal network directly? >> > >well, that's not case. But even then, how can a ISP assign a complete C >network just like this? What's behind that? the ISP is assigning IPs based on a block of IPs they already own, they don't just "create" them. They'll block off part of their own class A or B network and allow you to use them. All IPs get assigned by a naming authority, such as ARIN.
