Have you ever thought too hard at made it more difficult than it is...please help

RS6RS6 Member Posts: 7 ■□□□□□□□□□
I know I'm thinking to deep into this but I need clarification

Ex. ROAS with 2 Vlans. Vlan 2 is part of x.x.0.0 /24 and Vlan 3 part of x.x.1.0/24. I want to verify that sub int for x.x.0.0 will have an IP address in x.x.0.0 as well as Vlan 3 having an ip address in x.x.1.0. I got that part but the physical port/trunk will have what subnet? It will be the only active interface on that subnet right ex on x.x.3.0 /24 network?


  • WillowWhispWillowWhisp Registered Users Posts: 1 ■□□□□□□□□□
    There isn't an IP number/subnet assigned to the router's physical interface which is used as the trunk. That's the whole point of configuring the subinterfaces! So, for example, assuming we're using subnetting the private Class C network, with VLAN 2 using the subnet and VLAN3 using the subnet, you just need to enable (no shut) the physical port that is being used as the trunk to your switch, then go in and configure the subinterfaces.

    Router(config)#interface f0/1 (This is your physical interface/trunk leading to the switch)

    Router(config-if)#no shutdown
    Router(config)#interface f0/1.1 (This is your subinterface for VLAN 2)

    Router(config-subif)#encapsulation dot1q 2 (the number after dot1q is the VLAN number)

    Router(config-subif)#ip address (this is the "default gateway" for the subnet)

    Router(config)#interface f0/1.2 (This is your subinterface for VLAN 3)

    Router(config-subif)#encapsulation dot1q 3

    Router(config-subif)#ip address (this is the "default gateway" for the subnet)
    You don't need to assign any addresses in the subnet. If you decide to do so, you should add another VLAN, for example VLAN 30, to associate it with:

    Router(config)#interface f0/1.3

    Router(config-subif)#encapsulation dot1q 30

    Router(config-subif)#ip address
  • lantechlantech Member Posts: 329
    The physical interface on the router won't have an IP address. Only the sub interfaces do.
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  • nole07nole07 Member Posts: 22 ■□□□□□□□□□
    The physical interface can have an ip address though. you can have an ip address for fa0/0, etc... and then the subinterfaces can all have ip addresses for their respective vlans.
  • RS6RS6 Member Posts: 7 ■□□□□□□□□□
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