4-9
Layer 3 Switching Software Feature and Configuration Guide
78-6235-04, Cisco IOS Release 12.0(10)W5(18)
Chapter4 Configuring Interfaces Configuring ISL VLAN Encapsulation
Figure 4-2 Example of an ISL VLAN Bridging Configuration
Toconfigure the Layer 3 VLANs shown in Figure 4-2, perform the following steps, beginning in global
configuration mode:
encap isl 50
encap isl 100
VLAN 50
VLAN 100
1/0/0
1/0/1.2
1/0/1.1
3/0/1
Bridge-group 2
Bridge-group 1
Campus
switch
router
Campus
switch
router
17489
Command Purpose
Step1 Router(config)# interface fastethernet
slot/subslot/interface.subinterface
Router(config-subif)#
Enters subinterface configuration mode.
Step2 Router(config-subif)# encapsulation isl vlan-id Specifies ISL encapsulation for the Ethernet
frames sent from this subinterface with a
header that maintains the specifiedVLAN ID
between network nodes.
Step3 Router(config-subif)# bridge-group bridge-group Assigns the subinterface a bridge group
number.
Note When you are configuring VLAN
routing, skip this step.
Step4 Router(config-subif)# interface fastethernet
slot/subslot/interface
Router(config-if)#
Enters interface configuration mode to
configure the Fast Ethernet main interface.
Step5 Router(config-if)# bridge-group bridge-group Assigns the main interface to the bridge
group.
Step6 Router(config-if)# exit
Router(config)#
Returns to global configuration mode.
Step7 Router(config)# bridge bridge-group protocol ieee Specifies that the bridge group will use the
IEEE Ethernet Spanning Tree Protocol.