Configuring ISL Trunks

Note:

The 1900 series switch supports only Inter-Switch Link (ISL) trunking. The 2900 series switch supports both ISL and Dot1Q trunking. The 2950 series switch supports only Dot1Q trunking.

1900 Series Switch

1900Switch(config)#int fa 0/26	Enters interface mode
1900Switch(config-if)#TRunk on	Turns trunking mode on

2900 Series Switch

2900Switch(config)#int fa 0/1	Enters interface mode
2900Switch(config-if)#switchport mode trunk	Turns port to trunking mode
2900Switch(config-if)#switchport trunk encapsulation isl	Sets encapsulation type to ISL

Note:

Trunking can only occur on a Fast Ethernet port. A 1900 series switch has only two Fast Ethernet portsports A and B. These are defined as fa 0/26 and FA 0/27 in the command-line interface (CLI).

Note:

For any series switch, you must set trunk mode at both ends of the link for the trunk to become active.