Configuring ISL Trunks


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


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).


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

CCNA Self-Study(c) CCNA Portable Command Guide
CCNA Portable Command Guide
ISBN: 1587201585
EAN: 2147483647
Year: 2006
Pages: 261
Authors: Scott Empson

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