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? （）
A.255.255.255.0 B.255.255.255.128 C.255.255.252.0 D.255.255.255.224 E.255.255.255.192 F.255.255.248.0
单项选择题 下列是外部网关路由协议的是（）。
单项选择题 IP地址中，网络部分全0表示（）。
单项选择题 On point-to-point networks, OSPF hello packets are addressed to which address（）。
