Consider IPv4 addressing and routing behavior. Which statement below is incorrect?

Difficulty: Medium

If a host moves from one network to another, its IP address must change (absent mobility mechanisms).
Routing uses the host portion of the IP address to choose the path to a destination.
An IP address designates a network attachment (interface) rather than the entire machine.
For a multihomed host, the path taken to it can depend on which of its addresses is used.
None of the above

Correct Answer: Routing uses the host portion of the IP address to choose the path to a destination.

Explanation:

Introduction / Context:
IPv4 addressing encodes both network and host information. Routers forward based on network prefixes, while end hosts care about the full address for local delivery.

Given Data / Assumptions:

Classless routing (CIDR) is in use.
Routers perform longest-prefix match on the destination network.
Hosts may be multihomed with multiple interfaces and addresses.

Concept / Approach:
The key distinction is that forwarding decisions are made on network prefixes (the network portion), not on the host portion. A statement claiming the opposite is incorrect.

Step-by-Step Solution:

1) Recognize that routers match destination network prefixes in FIB/RIB.2) Host-specific routes exist but are exceptional; general routing uses network portion.3) Evaluate each option and identify the one contradicting this behavior.

Verification / Alternative check:
Observe routing tables: entries are prefixes (e.g., 203.0.113.0/24), not individual hosts, confirming network-based decisions by default.

Why Other Options Are Wrong:

Option A is correct for typical IPv4 without mobility tunneling.Option C is correct: addresses bind to interfaces (network attachments).Option D is correct: different destination addresses can traverse different paths or hit different policies.“None of the above” is wrong because one statement (option B) is indeed incorrect.

Common Pitfalls:
Assuming routers examine host bits for path choice; conflating ARP/ND (local delivery) with inter-network routing.

Final Answer:
Routing uses the host portion of the IP address to choose the path (incorrect).

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Consider IPv4 addressing and routing behavior. Which statement below is incorrect?

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