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Thread: routers??

  1. #21
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    - user0182

  2. #22
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    Quote Originally Posted by user0182
    as most of the time sending to an IP address or a MAC address on a LAN has the same effect.
    Try adding a router to the equation. Look what happens to the MAC addresses once a packet crosses a router.

    i thought that a switch is a series of bridges, and each bridge learns the MAC addresses that are on either side of itself (i.e. operating at layer 2 of OSI), and thus only transmits packets where the source and destination MAC addresses are on different sides of the bridge. am i correct?
    That sounds about right.
    Oliver's Law:
    Experience is something you don't get until just after you need it.

  3. #23
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    i think that basically my question is; can a switch deal with more than one MAC address connected to it's interfaces?

    for instance; if one were to connect a hub to a switch or another switch to a switch.

    so, i am also wondering what is the difference between a switch's normal interfaces and an "uplink" interface?

  4. #24
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    Quote Originally Posted by user0182
    i think that basically my question is; can a switch deal with more than one MAC address connected to it's interfaces?
    Yes, it can. They're stored in what's known as a CAM table.
    http://en.wikipedia.org/wiki/CAM_Table

    so, i am also wondering what is the difference between a switch's normal interfaces and an "uplink" interface?
    As I've said before, RxD and TxD are reversed and for the more expensive switches the speed is usually higher (1Gbit uplink vs. 100Mbit ports).
    Oliver's Law:
    Experience is something you don't get until just after you need it.

  5. #25
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    i still don't quite understand. i am assuming that by "RxD and TxD are reversed"; you mean that the actual wires in the socket are reversed?

    if so, i don't understand why the wires have to be reversed, could you explain?


    regards,

    - user0182

  6. #26
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    Normally TxD is pin 1 and 2 and RxD is on 3 and 6.

    1) TxD+
    2) TxD-
    3) RxD+
    4)
    5)
    6) RxD-
    7)
    8)

    What would happen if you used a straight (1-to-1) cable to connect two similar ports together?
    RxD on one side will be connected to RxD on the other. Same for TxD. This won't work.

    If RxD and TxD are reversed RxD on the one side will be connected to TxD on the other and vise versa.
    So either RxD/TxD need to be reversed on the device itself or you'll need to use a crosscable.
    Oliver's Law:
    Experience is something you don't get until just after you need it.

  7. #27
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    okay, so i now understand where crossover cables come into the equation.

    so now let me just test my knowledge. if, for instance, you have a standard switch with only 4 standard interfaces and no uplink interface, and you connect 4 clients to a hub and connect the hub to one of the switch's interfaces (all with straight cables), then you connect 2 clients to 2 of the switch's other interfaces (with straight cables), and finally connect the remaining switch interface to another switch's standard interface with a crossover cable. does this sound as though it would probably work?

    btw: is there an easy way to tell different port types apart (i.e. standard from uplink)?


    regards,

    - user0182

  8. #28
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    If the hub doesn't have an uplink port you'll need to use a crosscable to connect it to the switch.

    And never forget to set the switch port to half duplex if you connect a hub to it!

    Uplink port is usually marked as such or with an X.. You find out quick enough as the link led won't come on..
    Oliver's Law:
    Experience is something you don't get until just after you need it.

  9. #29
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    thanks SirDice, that has been really helpful, i think that my knowledge is getting much better. i was also wondering, is there a convention from marking auto-sensing ports, or is it just a matter of reading the documentation?

    i was also wondering; when one has a router that is connected to the Internet, how does that router know where to route packets that are not addressed to IP addresses on one's LAN? does one's router send all of these packets to a default IP address of a router at one's ISP?


    regards,

    - user0182
    Last edited by user0182; July 28th, 2008 at 04:23 PM.

  10. #30
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    Quote Originally Posted by user0182
    i was also wondering, is there a convention from marking auto-sensing ports, or is it just a matter of reading the documentation?
    RTFM works for me

    i was also wondering; when one has a router that is connected to the Internet, how does that router know where to route packets that are not addressed to IP addresses on one's LAN?
    The (static) routing table defines were to route things. Try (on windows or *nix) netstat -rn.

    There can be some dynamic routing too. Things like RIP, OSPF and BGP.
    Oliver's Law:
    Experience is something you don't get until just after you need it.

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