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Why do ISPs use VLANs?

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  • 09-06-2023 9:51am
    #1
    Glaceon
    Registered Users Posts: 2,085 ✭✭✭


    I know all of the fibre and VDSL ISPs here make use of VLAN tagging but I never asked myself why until now. Is it done for isolation between the WAN and LAN or something completely different?



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    #2
    murphaph
    Registered Users Posts: 19,018 ✭✭✭✭murphaph


    I guess some ISPs use them to identify different services, like TV, Internet, Phone. Many also use them to route packets to and from the correct ISP where the line is used by multiple ISPs. Imagine you have VDSL. How does the infrastructure know that you are an eir customer and not an O² customer. The PPPoE login stuff is only known by you and your ISP, not by the infrastructure between you and the ISP, so there needs to be some way to get your packets to the correct ISP in the first place. That's how it is here in Germany anyway.



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    #3
    smuggler.ie
    Registered Users Posts: 4,113 ✭✭✭smuggler.ie


    https://www.boards.ie/discussion/2058300069/why-do-isps-use-vlans

    Interesting question to have an answer to...

    https://www.boards.ie/discussion/comment/120719128#Comment_120719128

    As you mention, i read IRL is somewhat different setup than DE (see #9)

    Perhaps here tag 10(other) used to identify the service, ISP is identified by other/different means...

    history of boards 2021




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