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  1. Hi Regina,

    The configuration on the Cisco switch is pretty straightforward. The interface connected to the router has to be a trunk:

    interface fa0/24
    description LINK_TO_ROUTER
    switchport mode trunk

    And the interfaces that connect to the host are regular access ports:

    interface fa0/1

    description HOST_IN_VLAN_10
    switchport mode access
    switchport access vlan 10

    You don’t need to use VLAN SVIs…a layer 2 switch uses the SVI only for management purposes. A layer 3 switch uses a SVI per VLAN which hosts can use as default gateway (in that case you don’t need a router on a stick anymore).


  2. Hi Rene/Moderators,

    What happens if I do not configure the sub interfaces?
    Would only intervlan routing be affected?
    What if they are on the same vlan?

  3. Hello Ian

    If you don’t configure subinterfaces on the router, then no tagged traffic will enter the interface. The switch is set up to send frames to the router using dot1q encapsulation. This is where the VLAN number of each specific frame is added to the header as a tag. When the router receives these frames, it will drop them because they include a tag. By adding subinterfaces and the appropriate dot1q encapsulation, you are allowing the router to be able to receive tagged frames and to allow them to egress on the appropriate subinterface.

    If communication between two devices on the switch that are on the same VLAN occurred, those frames would never reach the router. This is because no routing is necessary since both devices are on the same subnet. So, same-VLAN communication would not be effected.

    I hope this has been helpful!


  4. Hi if any rate limit configuration needs to be done on the interface we should do in interface level or sub interface level

  5. Question. I see you created sub-interfaces on the routers 0/0 interface. I understand that. But what if you did not use sub-interfaces. What if instead you assigned Router Fa0/0 to ip address and you assigned Router interface fa0/1 to ip address So two connected routes (2 separate IP addresses) on the router connected to the same single switch (switch is divided into VLAN 10 and VLAN 20). Would that work?

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