For security reasons, the network administrator needs to prevent pings into the corporate networks from hosts outside the internetwork. Which protocol should be blocked with access control lists？（）

A.ping
B.Telnet
C.FTP
D.TCP
E.IP

A.denial of service
B.brute force
C.reconnaissance
D.Trojan horse 

A.This command should be executed from the global configuration mode.
B.The IP address 10.121.16.8 is the local router port used to forward data.
C.102 is the remote DLCI that will receive the information.
D.This command is required for all Frame Relay configurations.
E.The broadcast option allows packets， such as RIP updates， to be forwarded across the PVC