Mailinglist Archive: opensuse (1826 mails)

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Re: [opensuse] Moving to IPv6
  • From: James Knott <james.knott@xxxxxxxxxx>
  • Date: Fri, 10 Sep 2010 00:24:40 -0400
  • Message-id: <4C89B308.6090307@xxxxxxxxxx>
John Andersen wrote:
See! There you go with that snark again.

When had I done that before or now. I was simply suggesting you might want to do some research to clear up some confusions.
With a globally unique address why do I need a router on the end of my cable
modem?

Lets go back to the beginning of the internet. Back then, there were a variety of network types, such as ethernet, token ring, arcnet and proprietary networks. The internet was intended to be a universal standard that could connect all these different networks. Each site was assigned a block of addresses for use on their networks. Now the problem became how to get from network A to network B. The solution was the router. The router on network A would have an address on that network that could talk to other devices on that network and the other side of the router would connect to the router on network B, which would likewise have an address on it's local network. The links themselves don't have an address. Now when a computer on network A wants to send a packet, it checks to see if the destination is on the local network. If so, it sends it directly over the local network. If the destination is not on the local network, it sends it to the appropriate router (there may be more than one router on a network) to be forwarded on to the remote network, where the router there sends the packet to another local device, which might even be another router. This is how communication around the world is possible.

As for whether or not you'll need a router, that depends on how your ISP delivers your subnet to you. Cable and DSL modems are generally configured to deliver a single address to the customer. With those, you'd need a router to connect to your network so that it could relay foreign packets, in the manner described above.. The other method would be for the ISP to do all your routing for you and connect to your network with what amounts to a bridge (bridges preserve MAC addresses, routers discard them), so that no routing would be required between you and the ISP. This way, their router would appear on your local lan, as though it were actually at your location. I have used this method to connect multiple sites via microwave, fibre, T1 or SHDSL, so that the customer would have a flat network, instead of separate subnets at each site. I have also set up many networks with traditional routing, often, but not always, with NAT. One customer had 5 sites with routing, but no NAT, connected via SHDSL. Another had 3 sites with a flat network, connected via microwave. Another had 3 sites with a flat network, connected via fibre.

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