sub interfaces

RUN-DMCRUN-DMC Member Posts: 35 ■■□□□□□□□□
Could someone simply describe why and when would you implement sub interfaces on a single physical interface? thanks just trying to grasp the conecpt. :D


  • netstatnetstat Member Posts: 65 ■■□□□□□□□□
    subinterfaces are a means of establishing multiple virtual links over a single physical one -which in turn makes up a virtual circuit.

    The easiest way i found to explain it would be by the example of vlans. Consider a switch which is divided into 3 vlans and 3 separate switches

    If u were actually using 3 switches u would need 3 cables running from each switch to a router. If instead u are using 3 vlans on the same switch, a single cable is required which runs between your router and your 3vlan-ed switch. This cable (configured and known as a TRUNK) will carry information as if it were 3 separate cables when using 3 separate switches. Therefore, for every "virtual cable" to a "virtual switch" a subinterface configuarion is required on the router.

    This is just a simple example, hope this helps.
  • netstatnetstat Member Posts: 65 ■■□□□□□□□□
    "which in turn makes up a virtual circuit."

    Ignore this part cos i went into frame-relay here.. which is not true for this example! sorry
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