What is the Extended System ID field in the STP Bridge ID?

The Extended System ID field in the Spanning Tree Protocol (STP) Bridge ID consists of 12 bits. This field is crucial as it helps in the unique identification of a switch within the spanning tree topology. The Bridge ID itself is a critical component in Spanning Tree Protocol, as it determines the root bridge and influences STP’s decisions on path selection and loop avoidance.

The Bridge ID is composed of a combination of the Bridge Priority and the MAC address of the switch. Specifically, the Bridge ID format is as follows: the first 4 bits represent the Bridge Priority, and the next 12 bits make up the Extended System ID. The Extended System ID allows for the support of larger VLANs within the STP implementation, accounting for the additional requirement that arises from having multiple VLANs. Thus, the correct answer reflects the proportion of the Bridge ID attributed to the Extended System ID, which is essential for proper functioning and operation of STP in complex network setups.