RE: [SLE] How to use a Linux System as a router?

From: Peer Stefan (stefan.peer_at_tiwag.at)
Date: 11/04/03

  • Next message: tallison_at_tacocat.net: "Re: [SLE] Suse Acquisition good/bad" 
    Date: Tue, 4 Nov 2003 16:11:38 +0100
To: "SuSE-Linux" <suse-linux-e@suse.com>

    Hi,
    > From: Darrell Cormier [mailto:linuxdev@sptc.net]
    > >I asked a similar question a few months agoin a thread cable
    > internet
    > >questions(9/23) ...
    > >Just a note on the home made router, there are lots of pre-stipped
    > >linux based router/firewall packages. Usually take between 300 and
    > >500mb and 32meg of ram. Clarkconnect is the only one that comes to
    > >mind right now.
    > >
    > >Switch v. Router. I haven't noticed much difference in the two
    > >personally, but I understand that the more traffic you have the more
    > >you want a switch. Switches direct traffic to a specific
    > machine and
    > >routers just route them along to all the machines. Thus increasing
    > >network traffic.
    > ><snip>
    > >
    > I am not a networking guru but this description sounds like the
    > difference between a Hub and a switch. It could be both but
    > I thought a
    > router routed directly to specific machines.
    >
    > Please correct me if I am wrong about this.

    Routers and switches work on different layers within the OSI layer model:

    1. PHY - this is the lowest layer. Physical connection, point to point
    2. MAC/DLL - Media Access/Data Link Layer: This is the "Switch"-layer. Switches "route" traffic according to their MAC-addresses.
    3. Network - This is where IP comes in, with subnetting and ip-routing and the whole thing. This is the "Router"-layer.
    4. Transport - TCP, UCP, et al.
    5. Session - deals with application-to-application communication
    6. Presentation or Syntax layer - converts incoming or outgoing data from one format to another
    7. Application - Mail, HTTP, whatever high-level application protocoll

    Basically a router connects two subnets, a switch is located within one subnet. Yes, there are so-called "Layer 3 Switches", which understand IP and there are routers, which understand the application layer (for at least some applications), but I think you get the idea.

    If you interconnect two or more subnets you'll need a router (e.g. your internet gateway) and if you connect some devices within one subnet a hub or a switch will do.

    Cheers,
    Stefan 

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