In which mode do Cisco switches operate by default for VLAN Trunking Protocol (VTP)?

Cisco switches operate in VTP server mode by default. In this mode, a switch can create, modify, and delete VLANs for the VTP domain. It also communicates VLAN information to other switches in the network that are in either client or server mode. This allows for centralized configuration management of VLANs across the network, streamlining operations and reducing the chances of configuration inconsistencies.

In VTP server mode, changes made on one switch are propagated to all other switches in the same VTP domain, ensuring that all switches share an up-to-date VLAN configuration. This seamless update mechanism simplifies network management, especially in larger environments where manually synchronizing VLAN configurations on multiple switches would be cumbersome and error-prone.

The other modes, such as transparent and client, do not offer the same capability for VLAN management. In transparent mode, a switch does not participate in VTP and doesn't propagate VLAN information to other switches, only forwarding VTP advertisements. In client mode, a switch receives VLAN information but cannot create or modify VLANs itself; it relies on the VTP server for updates. This hierarchy emphasizes the pivotal role of VTP server mode within a network’s VLAN management architecture.