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| 2.5 |  | VLAN Trunking and Dynamic Trunking Protocol (DTP) |
| 2.5.7 |  | Verifying DTP |

The show interface switchport command can be used to verify DTP information and status:

- Administrative Mode
- Operational Mode
- Administrative Trunking Encapsulation
- Negotiation of Trunking

The Administrative Mode displays the DTP state of the interface. The default on most Cisco switches is dynamic desirable. The DTP mode can be set using the switchport mode interface command.

The Operational Mode shows whether the interface is in a trunking or non-trunking state. If the Operational Mode is static access, then this interface considers the link as non-trunking. If the Operational Mode is trunk, then this interface is considered a trunking link. The show interface trunk command can be used to display all of the interfaces on the switch that have an Operational Mode set as trunk.

The Administrative Trunking Encapsulation displays the trunking protocol, 802.1Q or ISL, that is used on this interface if it the Operational Mode is in a trunking state. If the Operational Mode of the switch is in static access, non-trunking, then the trunking protocol that is Administrative Trunking Encapsulation displays is not currently being used on the link.

The Negotiation of Trunking shows whether the interface is willing to negotiate trunking by sending DTP frames. By default, the interface will negotiate trunking and the Negotiation of Trunking will show as On. The switchport nonegotiate interface command is used to turn off this negotiation.