Router on a stick

Router on a stick

How to configure Router on a stick?

creating subinterfaces 

fa 0/0.10 and fa 0/0.20, the config looks like this

interface fastethernet 0

no ip address

no shut

interface FastEthernet 0/0.10

encapsulation dot1q 10

ip address 10.10.10..1 255.255.255.0

no shut

interface FastEthernet 0.20

encapsulation dot1q 20

ip address 20.20.20.1 255.255.255.0

no shut


Note;
*most common error with router-on-a-stick is put the wrong VLAN number in the encapsulation statement.

*this "sub-interfaces" concept also apply in 
- FRAME RELAY  
- VRF
- and FIREWALL

we can replace the Router with a Layer 3 switch, see inter vlan routing with Layer 3 switch