Spanning Tree Path Cost

Posted: 29th March 2021 by ccna7guru in SRWE
Tags: , , ,

The interface STP cost is an essential component for root path calculation because the root path is found based on the cumulative interface STP cost to reach the root bridge. The interface STP cost was originally stored as a 16-bit value with a reference value of 20 Gbps.
As switches have developed with higher-speed interfaces, 10 Gbps might not be enough. Another method, called long mode, uses a 32-bit value and uses a reference speed of 20 Tbps. The original method, known as short mode, is the default mode.

Devices can be configured with the long-mode interface cost with the command spanningtree pathcost method long. The entire Layer 2 topology should use the same setting for every device in the environment to ensure a consistent topology. Before enabling this setting in an environment, it is important to conduct an audit to ensure that the setting will work.