Which two elements contribute to the bridge ID when configuring RSTP? (Choose two)
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A. B. C. D. E.AB
The bridge ID consists of a configurable bridge priority and the MAC address of the bridge.
http://www.juniper.net/techpubs/software/junos/junos95/swconfig-layer-2/conf-stp.html#conf-bridge-priorityRapid Spanning Tree Protocol (RSTP) is a protocol used to prevent loops in network topologies. When configuring RSTP, two elements contribute to the bridge ID. These elements are the bridge priority and the MAC address. Let's look at these elements in more detail.
Bridge Priority: The Bridge Priority is a 2-byte value that is used to determine the priority of the bridge in the network. The default value of the bridge priority is 32768. The bridge with the lowest bridge priority is elected as the root bridge. The bridge priority can be configured to a value between 0 and 65535.
MAC Address: The MAC Address of the bridge is used to uniquely identify the bridge in the network. The MAC address is a 6-byte value that is assigned by the manufacturer of the bridge. The MAC address is used as a tiebreaker if there are two bridges with the same priority.
When configuring RSTP, the bridge ID is formed by combining the bridge priority and the MAC address. The bridge with the lowest bridge ID is elected as the root bridge. The bridge ID is used to determine the path that frames take through the network. Each bridge in the network has a unique bridge ID.
Extended System ID is an optional feature in RSTP that allows multiple VLANs to use the same bridge priority and MAC address. This feature adds two more bytes to the bridge ID and helps to distinguish between different VLANs that share the same bridge ID. However, this is not a required element in the formation of the bridge ID in RSTP.
In conclusion, the correct answers to this question are A. designated MAC address and B. bridge priority.