What is the default hello timer for STP?

The Spanning Tree Protocol (STP) uses "hello" messages to maintain the topology of the network by ensuring that switches are aware of each other and their connections. The default hello timer, which defines the frequency at which these hello messages are sent, is set to 2 seconds.

This timer is crucial because it helps switches quickly detect changes in the network topology, such as a failed connection or the introduction of a new switch. A shorter hello interval allows for faster convergence times, meaning the network can react more swiftly to changes. While there are other timers in STP, such as the forward delay and max age timers, the hello timer specifically determines how often switches communicate to maintain the STP topology.

This understanding of the default hello timer helps network administrators configure and troubleshoot STP effectively, ensuring that the network remains loop-free and stable.