Command:

encapsulation isl


Mode:

Router(config-subif)#


Syntax:

encapsulation isl vlan-identifier

no encapsulation isl

Syntax Description:

 

vlan-identifier

This represents a VLAN identifier that has an allowed range from 1 to 1000.


Command Description:

To enable the Inter-Switch Link (ISL), use the encapsulation isl command in subinterface configuration mode.

ISL is a Cisco protocol for interconnecting multiple switches and routers, and for defining VLAN topologies.

ISL encapsulation is configurable on Fast Ethernet interfaces.

ISL encapsulation adds a 26-byte header to the beginning of the Ethernet frame. The header contains a 10-bit VLAN identifier that conveys VLAN membership identities between switches.


Example:

 

The following example sets subinterface fastethernet 2/1.20 for trunking protocol of ISL:

Router(config)#interface FastEthernet 2/1.20 
Router(config-subif)#encapsulation isl 400


Misconceptions:

 

None


Related Commands:

 

encapsulation dot1q

 


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