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Networking Fundamentals · Foundational

Hop Limit

The 8-bit IPv6 header field, equivalent to the IPv4 TTL, decremented by each router and discarded at zero.

Definition

When the hop limit reaches zero, the router drops the packet and sends an ICMPv6 Time Exceeded message. Traceroute for IPv6 uses it to discover hops. Some Neighbor Discovery messages must be sent with a hop limit of 255 so receivers can verify they came from the local link.

Example

Linux hosts send IPv6 packets with a default hop limit of 64.

Exam tip

Hop Limit = TTL renamed; same function.

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