1900 Series Switch
1900Switch#show trunk A
Displays trunking information about port 0/26
DISL state: On, Trunking: On, Encapsulation type: ISL
1900Switch#
2900 and 2950 Series Switches
29x0Switch#show int fa 0/1 switchport
Shows the status of the interface, including trunking information
Name: Fa0/1
Switchport: Enabled
Administrative mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: isl
Operational Trunking Encapsulation: isl
<output cut>
29x0Switch#