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| 2.5 |  | VLAN Trunking and Dynamic Trunking Protocol (DTP) |
| 2.5.4 |  | Basics of Dynamic Trunking Protocol (DTP) |

Ethernet trunk interfaces support several different trunking modes.

- Access
- Dynamic desirable (default mode on Catalyst 2950 and 3550)
- Dynamic auto
- Trunk
- Non-negotiate
- dotq-tunnel (Not an option on the Catalyst 2950.)

Using theses different trunking modes, an interface can be set to trunking or nontrunking or even able to negotiate trunking with the neighboring interface. To automatically negotiate trunking, the interfaces must be in the same VTP domain. Trunk negotiation is managed by the Dynamic Trunking Protocol (DTP), which is a Cisco proprietary Point-to-Point Protocol.

These various modes are configured using the switchport mode interface command as shown in Figure . Figure shows the various DTP modes.