VTP (VLAN Trunking Protocol) is the protocol that reduces administrative overhead in a switched network by allowing the configuration of a new VLAN to be distributed to all the switches in a domain.

Overview of VTP:
- VTP is a Cisco proprietary protocol that operates at layer 2 of the OSI model.
- It is used to manage VLAN configurations in a switched network.
- VTP allows for the creation, deletion, and renaming of VLANs on a Cisco switch.
- It also synchronizes VLAN information across all switches in a VTP domain.

Benefits of VTP:
1. Reduced administrative overhead: VTP simplifies the management of VLANs by allowing the configuration of a new VLAN to be distributed to all switches in a domain. This eliminates the need to manually configure VLANs on each switch individually, reducing administrative overhead and saving time.

2. Consistency: VTP ensures that VLAN configurations remain consistent across all switches in a domain. When a new VLAN is created or a VLAN is modified on one switch, the change is automatically propagated to all other switches in the domain. This helps maintain a consistent VLAN configuration throughout the network.

3. Scalability: VTP allows for easy scalability of VLANs. When a new switch is added to the network, it can automatically receive the VLAN configurations from other switches in the domain. This simplifies the process of expanding the network and adding new devices.

4. Security: VTP supports authentication, which provides an additional layer of security. By enabling authentication, only switches with the correct VTP password can participate in VTP updates. This helps prevent unauthorized switches from affecting the VLAN configuration.

VTP Modes:
VTP operates in three different modes:
1. Server mode: In this mode, VLANs can be created, modified, and deleted. The VLAN configuration changes made on a switch in server mode are propagated to all other switches in the domain.
2. Client mode: In this mode, VLANs cannot be created, modified, or deleted. The VLAN configuration changes made on a switch in client mode are received from the VTP server and applied to the switch.
3. Transparent mode: In this mode, VLANs can be created, modified, and deleted. However, the VLAN configuration changes are not propagated to other switches in the domain. This mode is typically used for switches that do not participate in VTP updates.

In conclusion, VTP reduces administrative overhead in a switched network by allowing the configuration of a new VLAN to be distributed to all switches in a domain. It simplifies VLAN management, ensures consistency, promotes scalability, and provides security through authentication.