Configuring Encapsulation

For VLAN information to be passed between switches, trunking must be configured between the switches. VLAN trunking allows a port to pass traffic from multiple VLANs between the two switches. Frames traveling over a trunk are tagged to identify to which VLAN the frames belong. When implementing trunking between switches, the ports at either end of the connection are set up for trunk mode, and the trunk encapsulation mode must match.

Trunk encapsulation dictates the manner in which frames are identified (tagged) on a trunk and defines the VLAN services available. To set the Encapsulation type as ISL (Inter-Switch Link) on the Interface, first set up the Port as trunk.Transmit hold count value is a counter used to limit the maximum transmission rate of the switch.

By default, the Dot1q Encapsulation is set.

Execute the following commands to set the Encapsulation type as ISL in the switch.
Type the following:
- Enter the Global Configuration Mode.
```
iS5comm# configure terminal
```
- Enter the Interface Configuration mode.
```
iS5comm(config)# interface gigabitethernet 0/1
```
- Configure the Port as Trunk Port.
```
iS5comm(config-if)# switchport mode trunk
```
- Set the Encapsulation type as ISL.
```
iS5comm(config-if)# spanning-tree encap ISL
```
```
Pvrst Encapsulation ISL is set.
```
- Return to the Privileged EXEC Mode.
```
iS5comm(config-if)#end
```
View the following output - verify if the encapsulation type is set as ISL on Port 1.
Type the following:
```
iS5comm# show spanning-tree interface gigabitethernet 0/1 encapsulationtype
```
```
Encapsulation Type is ISL
```
Note:
Execute the no spanning-tree encap Interface Configuration Mode command to set the Encapsulation type as Dot1q on the interface.
```
iS5comm(config-if)# no spanning-tree encap
```
```
Pvrst Encapsulation Dot1q is set.
```