Cisco CCNA 200-301 Practice Question

Using an extended access control list applied close to the source is the best approach. Extended access control lists can filter traffic based on source and destination IP addresses, protocols, and port numbers, which is necessary to block Telnet traffic (TCP port 23). Placing the extended list close to the source prevents unwanted Telnet traffic from traversing the network, enhancing efficiency. Standard access control lists only filter based on source IP addresses and should be placed close to the destination, so they are not suitable for this scenario. Applying an extended list close to the destination is less efficient as it allows unnecessary traffic onto the network.