At which layer of the OSI model is RSTP used to prevent loops?
A.
physical
B.
data link
C.
network
D.
transport
Explanation:
RSTP and STP operate on switches and are based on the exchange of Bridge
Protocol Data Units (BPDUs) between switches. One of the most important fields in BPDUs is the
Bridge Priority in which the MAC address is used to elect the Root Bridge , RSTP operates at
Layer 2.
http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cfa.shtml