RIP (Routing Information Protocol) would be the least suitable for large-scale networks due to its limitation in hop counts. RIP uses hop count as a metric, which can lead to routing loops and suboptimal paths in large networks. More advanced protocols like OSPF, EIGRP, and BGP are better suited for large-scale environments.

FTP (File Transfer Protocol) data transfer is commonly secured using TLS (Transport Layer Security) encryption. This encryption ensures that data sent over FTP is protected from eavesdropping and tampering, making it a safer choice for transferring sensitive information.

ARP Poisoning (Address Resolution Protocol Poisoning) is an attack where the attacker associates their MAC address with the IP address of another machine, potentially leading to network disruption or interception of data.

DNS (Domain Name System) is responsible for translating human-readable domain names, like www.example.com, into IP addresses that computers use to identify each other on a network. DNS acts as the internet's "phonebook."

The most suitable tool for checking the IP address associated with a domain name is "nslookup." This command-line tool is used to query DNS (Domain Name System) servers to obtain information about domain names, including their corresponding IP addresses. It's a valuable tool for troubleshooting network connectivity issues.

The Application, Presentation, and Session layers of the OSI model correspond to the Application layer in the TCP/IP model. The Application layer in the TCP/IP model is responsible for providing network services directly to applications. It serves as the interface between software applications and the network stack, handling tasks such as data encryption and decryption, data compression, and application-level protocols.

BGP (Border Gateway Protocol) is the protocol John is likely considering. BGP is well-known for its route stability and supports complex policy-based routing decisions. It's a good choice for networks where route stability is crucial.

Virtual LAN (VLAN) is a solution that can segregate a network into smaller, isolated segments, even if they share the same physical infrastructure. This helps reduce broadcast traffic and allows different departments to communicate efficiently while maintaining network security.

Immunity to Eavesdropping - Fiber optic cables offer a high level of data security because they transmit data as light pulses, and it's extremely difficult to intercept these signals without disrupting the communication. Unlike other mediums where electromagnetic signals can be intercepted, fiber optic cables are more secure against eavesdropping.

TCP (Transmission Control Protocol) offers a built-in mechanism for ensuring data integrity. It does this by using techniques such as error-checking and acknowledgments to confirm that data is received correctly. TCP is a connection-oriented protocol that provides reliable data delivery.