CCNA: InterVLAN Switching

1 minute read

Description:

InterVLAN communications require a Layer 3 device. The most common is a “router on a stick” setup.

Router On A Stick Setup:

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   Router(config)#int fa0/0
   Router(config-if)#switchport mode trunk
   Router(config-if)#switchport trunk native vlan 99
   Router(config)#int fa0/0
   Router(config-if)#no shut
   #On the router create subinterfaces on the same trunk interface with the respective subnets for the associated VLAN it will route.
   #Match the subinterface number with the VLAN number to make life easy.
   #For example, VLAN2
   Router(config)#int fa0/0.2
   Router(config-if)#encap dot1q 2
   Router(config-if)#ip address 192.168.2.1 255.255.255.0
   #VLAN3
   Router(config)#int fa0/0.3
   Router(config-if)#encap dot1q 3
   Router(config-if)#ip address 192.168.3.1 255.255.255.0
   #Native VLAN
   Router(config)#int fa0/0.99
   Router(config-if)#encap dot1q 99 native

Cisco Website:

  • 3 steps: Create VLANs you want to route, give them IP’s, and assign a default gateway
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   Switch#vlan database
   Switch(vlan)#vlan 2
   Switch(vlan)#vlan 3
   Switch(vlan)#vlan 10
   Switch(vlan)#exit
   Switch#configure terminal
   Switch(config)#ip routing # this tells the switch to do the routing between vlans
   Switch(config)#interface Vlan2
   Switch(config-if)#ip address 10.1.2.1 255.255.255.0
   Switch(config-if)#no shutdown
   Switch(config)#interface Vlan5
   Switch(config-if)#ip address 10.1.5.1 255.255.255.0
   Switch(config-if)#no shutdown
   Switch(config)#interface Vlan10
   Switch(config-if)#ip address 10.1.10.1 255.255.255.0
   Switch(config-if)#no shutdown
   # Configure Default Route
   Switch(config)#ip route 0.0.0.0 0.0.0.0 200.1.1.2
   Switch(config)#interface FastEthernet 0/1
   Switch(config-if)#no switchport
   Switch(config-if)#ip address 200.1.1.1 255.255.255.0
   Switch(config-if)#no shutdown

Show Commands:

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   show interfaces f0/0 switchport
   show interface
   show ip interface
   show run
   show ip route

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