Comment on Merry ChristmaX

c0mbatbag3l@lemmy.world ⁨9⁩ ⁨months⁩ ago

• MadhuGururajan@programming.dev ⁨9⁩ ⁨months⁩ ago

  Are you just throwing networking terms together? How does a LAG prevent a switching loop?

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  • InEnduringGrowStrong@sh.itjust.works ⁨9⁩ ⁨months⁩ ago

    LAG are aggregated interfaces and they can indeed be used to prevent (some) layer 2 loops. LAG as in Link Aggregation Group)

    Using 2 non-LAG interfaces between the same 2 devices creates a loop.
    In the case of a loop, if you’re running spanning tree, one of these interface will be blocking instead of forwarding, preventing the loop, but also percentile the use of this interface until the topology changes (ie: the current one goes down).
    If you’re not running spanning tree for some reason, then both interface will chug along, oblivious to the fact that there’s a loop and broadcast packets will indeed keep being flooded on one and received on the other, again flooded, etc. creating a broadcast storm and impacting performance of the whole layer 2 domain and possibly even crashing devices.

    A LAG more or less means the interfaces in the group behave as one big (aggregated) interface.
    LAG also means you can push traffic on both interfaces for more bandwidth.

    Source: Network engineer Internet plumber

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  • c0mbatbag3l@lemmy.world ⁨9⁩ ⁨months⁩ ago

    It doesn’t.

    The assumption is that they’re creating a high bandwidth trunk interface to the router, so if they forget to create an aggregate it’ll be two independent interfaces and will down the network (or a port will auto down itself with STP, MSTP, etc. but that’s not as funny)

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    • MadhuGururajan@programming.dev ⁨8⁩ ⁨months⁩ ago

      A router of industrial scale which i see at work has its ports to be l3 ports by default. They don’t down the network as the router rejects config where two ports are given the same subnet… at least the ones i operate at work.

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      • c0mbatbag3l@lemmy.world ⁨8⁩ ⁨months⁩ ago

        That’s true, the default for layer 3 switches is to have its port set as routable.

        The original joke really kinda falls flat with modern tech, but it’s still funny to think about handing a switch to someone with zero knowledge and then watch as they accidentally lock up the environment.

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