Layer 3 sub-interface - Cisco

    Layer 3 sub-interface - Cisco

    Technology: Network
    Area: Configuration General
    Vendor: Cisco
    Software: 12.X, 15.X
    Platform: ISR Routers, ASR Routers

    Sub-interfaces divide the parent interface into two or more virtual interfaces on which you can assign unique Layer 3 parameters such as IP addresses and dynamic routing protocols parameters. The IP address for each sub-interface should be in a different subnet from any other sub-interface on the parent interface (if you are not using VRF-Lite feature).

    Switch# configure terminal
    switch(config)# interface ethernet 2/1.1
    switch(config-if)# ip address
    switch(config-if)# encapsulation dot1Q 66

    Because sub-interfaces work always on trunk links, there is a necessity of encapsulation definition. The encapsulation command defines the VLAN tag (VLAN number) which will be using by this sub-interface.

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