To enable NetFlow on a Cisco router interface, the correct command is ip route-cache flow, which is entered in interface configuration mode. This command enables NetFlow switching on the specified interface. NetFlow is a feature that captures IP network traffic as it enters or exits an interface. By analyzing the data provided by NetFlow, a network administrator can determine things like the source and destination of traffic, class of service, and the causes of congestion1.

Single key encryption uses a single word or phrase as the key. The same key is used by the sender to encrypt and the receiver to decrypt. Sender and receiver initially need to have a secure way of passing the key from one to the other. With TLS or SSL this would not be possible. Symmetric encryption is a type of encryption that uses a single key to encrypt and decrypt data. Symmetric encryption algorithms are faster than public key encryption. Therefore, it is commonly used when a message sender needs to encrypt a large amount of data. Data Encryption Standard (DES) uses the symmetric encryption key algorithm to encrypt data.