VLANs, trunking, STP/RSTP/MST, EtherChannel/LACP, first-hop redundancy protocols, and Layer 2 security.
Link aggregation, load balancing, port-channel configuration
HSRP, VRRP, GLBP — gateway high availability
Port security, DHCP snooping, DAI, storm control
Loop prevention, convergence, root bridge election
VLAN assignment, 802.1Q, native VLAN, inter-VLAN routing