An administrator issues the command ping 127.0.0.1 from the command line prompt on a PC. If a reply is received, what does this confirm（）。

A.Addresses are allocated after a negotiation between the server and the host to determine the length of the agreement.
B.Addresses are assigned for a fixed period of time.At the end of period,a newquest for an address must be made,and another address is then assigned.
C.Addresses are leased to host.A host will usually keep the same address by periodically contacting the DHCP sever to renew the lease.
D.Addresses are permanently assigned so that the host uses the same address at all times.

A.允许unrestricted访问到console或VTY口
B.用防火墙去限制外网的网络设备访问
C.因为数据被自动加密，所以总是允许使用TELNET命令访问网络设备的命令行
D.使用SSH或其他加密、认证机制去访问设备的配置
E.为了避免丢失密码，所以不对密码进行加密（明文）

A.It creates a global address pool for all outside NAT transactions
B.It establishes a dynamic address pool for an inside static address
C.It creates dynamic source translations for all inside local PAT transactions
D.It creates a one-to-one mapping between an inside local address and an inside global address
E.It maps one inside source address to a range of outside global addresses