How can a network administrator modify an ACL to include FTP transfers from any source IP address?

To include FTP transfers from any source IP address in an access control list (ACL), the option to add FTP rules after the existing ACL is effective because it allows the network administrator to modify existing rules without disrupting the flow of current configurations. By appending the new FTP rules, the administrator ensures that the ACL explicitly permits FTP traffic while maintaining any other configured rules that may apply.

This method is necessary because ACLs are processed in a top-down manner. If FTP rules are added at the correct position, they will be evaluated in conjunction with any pre-existing rules. This preserves the overall traffic management strategy that has already been implemented.

Creating a new access list would be a valid approach, but it could lead to more complexity in managing multiple ACLs, which is not as efficient as simply modifying the existing one. Denying all other traffic might inadvertently block legitimate services that should be allowed, and removing the existing ACL would completely eliminate all traffic rules, which could cause significant disruption to the network. Thus, adding FTP rules in the appropriate location ensures controlled access while keeping the existing ACL intact.