The network shown in the figure below. Two switches are connected by four links. COPPER refers to electrical interface and FIBER refers to optical interface. Then which two interfaces can realize link aggregation? () (Single-choice question)

Neither the A1 ternate interface nor the Backup port in RSTP can forward user traffic, nor can they receive, process, and forward BPDUs ()

The function of the 0SPF hel1o message is ()

Which of the following 0SPF protocol packets can ensure the reliability of LSA update? ()

What is wrong about the ARP message? ()