- Last Updated: Tuesday, 18 December 2018 07:35
VLAN management is quite different on ISR routers than on Catalyst switches. VLAN can be used as 802.1q subinterfaces for routed interfaces or with a switch-like configuration on Ethernet Switch Modules (HWIC-4ESW for example)
Subinterface configuration (routed interfaces)
Layer 3 router interfaces cannot be configured in switch mode using "switchport" command on a Cisco ISR router. However, 802.1q trunks interconnexion is supported on these interfaces using the subinterface feature.
Virtual layer 3 interfaces are bound to the physical port using the interface <interface name>.<inderface id> command, <interface id> beeing the subinterface ID. For better configuration readability, the <interface id> is usually configured with the <vlan id> value. The encapsulation dot1Q <vlan id> maps the trafic flowing with the 802.1q vlan id (tagged) to the subinterface.
In the example below, FastEthernet0/0.20 is a subinterface bound to the FastEthernet0/0 physical interface. FastEthernet 0/0.20 is configured to process trafic flowing on vlan 20 in the 802.1q trunk connected to the FastEthernet 0/0 physical router interface.
encapsulation dot1Q 20
ip address 10.20.10.1 255.255.255.0
encapsulation dot1Q 30
ip address 10.30.10.1 255.255.255.0
VLAN database (ESW module)
If an EtherSwitch Service Module (HWIC-4ESW for example) has been installed on the ISR router, VLAN for that module can be configured using the vlan database in Packet Tracer 7.2. Port membership to the vlan is configured in the same way than on a Catalyst switch using the "switchport access vlan <vid>" commmand.
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