CCNA: InterVLAN Switching

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Description:

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

Router On A Stick Setup:

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

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:

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

 

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