Consider a network where a packet is sent from Host A to Host B. The packet has an initial hop limit of 10. The packet passes through 3 routers before reaching Host B. Each router decrements the hop limit by 1. What is the remaining hop limit of the packet when it reaches Host B?

Correct option is A

The hop limit in a network packet specifies the maximum number of hops (routers) the packet can pass through before being discarded. Each router along the path decrements the hop limit by 1.
· Initial hop limit = 10
· Number of routers = 3
· Remaining hop limit = Initial hop limit - Number of routers
Remaining hop limit = 10 - 3
Remaining hop limit = 7
Thus, the packet will have a remaining hop limit of 7 when it reaches Host B.
Important Key Points:
1. Hop Limit Definition:
· The hop limit is part of the IPv6 header and is equivalent to the TTL (Time-to-Live) field in IPv4.
· It ensures that packets do not loop indefinitely in the network.
2. Decrementing Rule:
· Each router decrements the hop limit (or TTL) by 1 as the packet passes through.
· If the hop limit reaches 0, the packet is discarded to avoid network congestion.
3. Calculation Formula:
Remaining Hop Limit=Initial Hop Limit−Number of Routers Passed Through
Knowledge Booster:
· If the initial hop limit is too low, the packet might not reach its destination because it could be discarded before arriving.
· TTL vs Hop Limit: In IPv4, this field is called Time-to-Live (TTL), but it does not measure time; it counts hops. In IPv6, it is aptly renamed to Hop Limit.
· Practical Example: In traceroute, the hop limit is set incrementally to discover each router in the path between the source and destination.