单项选择题
A.ipv6 address PREFIX_1::1/64
B.ipv6 autoconfig 2001:db8:2222:7272::72/64
C.ipv6 autoconfig
D.ipv6 address 2001:db8:2222:7272::72/64
单项选择题 Which IPv6 address is valid?（）
单项选择题 which address range efficiently summarizes the routing table of the addresses for router main?（）
多项选择题 A national retail chain needs to design an IP addressing scheme to support a nationwide network. The company needs a minimum of 300 sub-networks and a maximum of 50 host addresses per subnet. Working with only one Class B address, which of the following subnet masks will support an appropriate addressing scheme?（）