CompTIA Network+ Practice Test

In IP networks, how is TTL measured?

1. In seconds

2. By data size

3. In hops

4. By packet type

The correct answer is: In hops

TTL, or Time to Live, is a value used in IP networking to specify the lifetime or hop limit of a packet as it moves through a network. It is primarily measured in hops, meaning that it indicates the maximum number of routers or hops a packet can pass through before it is discarded. Each time the packet is processed by a router, the TTL value is decremented by one. When the TTL value reaches zero, the packet is no longer forwarded and is dropped, helping prevent packets from circulating indefinitely in the network. This mechanism is vital for managing routing loops and ensuring efficient use of network resources. While the other options relate to aspects of networking, they do not correctly describe how TTL functions. For instance, measuring TTL in seconds would imply a time-based expiration, which is not how the protocol is designed to operate. Similarly, data size and packet type do not dictate the lifetime of a packet in the way hops do. Hence, understanding TTL as being measured in hops is fundamental for grasping how packets are managed and routed in IP networks.