Cisco Certified Network Associate (CCNA) Practice Exam

What is the primary function of Generic Routing Encapsulation (GRE) in networking?

1. To provide security for data transmission

2. To encapsulate various protocols into an IP tunnel

3. To assign IP addresses dynamically

4. To manage traffic flow using QoS

The correct answer is: To encapsulate various protocols into an IP tunnel

The primary function of Generic Routing Encapsulation (GRE) is to encapsulate various protocols into an IP tunnel, which enables the transparent transmission of packets through an IP-based network. GRE allows for the encapsulation of a wide variety of Layer 2 and Layer 3 protocols, including Ethernet, IPX, and others, inside a GRE packet. This encapsulation is particularly useful for connecting separate networks, allowing for the creation of virtual private networks (VPNs) and facilitating the transmission of data between different network protocols over an IP network. By creating a tunnel, GRE enables different networks using dissimilar protocols to communicate as if they were on the same network. This makes GRE an essential tool for network engineers who need to connect multiple sites, ensuring that data packets can traverse different types of networks without requiring significant changes to the underlying infrastructure. The other options focus on aspects that GRE does not cover. For example, offering security for data transmission requires additional protocols like IPsec, while dynamic IP addressing is managed by protocols such as DHCP, and quality of service (QoS) pertains to managing bandwidth allocation and traffic prioritization rather than encapsulation. Thus, the encapsulation ability of GRE stands out as its key function in networking.