How the Router Distinguishes Between VLANs (802.1q)

Each subinterface is then configured with the following two commands:

• encapsulation dot1q vlan_id 
• ip address ip-address subnet-mask 

Since there is only 1 physical Interface in a Router-on-a-Stick Configuration the router needs a new way to determine how to route traffic

This method is the IEEE 802.1q Subinterface tag

Although not required, it is customary to match the subinterface number with the VLAN number

The native keyword option is only appended to set the native VLAN to something other than VLAN 1

g0/0/1

f0/5

interface g0/0/1.10

encapsulation dot1q 10

ip address 192.168.10.1 255.255.255.0

interface g0/0/1.20

encapsulation dot1q 20

ip address 192.168.20.1 255.255.255.0

interface g0/0/1.99

encapsulation dot1q 99

ip address 192.168.99.1 255.255.255.0