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3.1.3. Inter-VLAN Connectivity
Devices in different VLANs require Layer 3 routing to communicate. Three options:
| Method | Description | Use Case |
|---|---|---|
| Router on a Stick | Single router interface with subinterfaces | Small networks |
| Layer 3 Switch (SVI) | Switch performs routing internally | Medium-large networks |
| External Router | Dedicated router with multiple interfaces | Legacy networks |
Router on a Stick Configuration:
Router(config)# interface GigabitEthernet0/0.10
Router(config-subif)# encapsulation dot1q 10
Router(config-subif)# ip address 192.168.10.1 255.255.255.0
Router(config-subif)# exit
Router(config)# interface GigabitEthernet0/0.20
Router(config-subif)# encapsulation dot1q 20
Router(config-subif)# ip address 192.168.20.1 255.255.255.0
Layer 3 Switch SVI Configuration:
Switch(config)# ip routing
Switch(config)# interface vlan 10
Switch(config-if)# ip address 192.168.10.1 255.255.255.0
Switch(config-if)# no shutdown
Switch(config-if)# exit
Switch(config)# interface vlan 20
Switch(config-if)# ip address 192.168.20.1 255.255.255.0
Switch(config-if)# no shutdown
Verification:
Switch# show vlan brief
Switch# show interfaces trunk
Switch# show interfaces GigabitEthernet0/1 switchport