Stub networks in routing: In computer networking and internetwork design, what is the best description of a stub network (i.e., a network that relies on a single path to reach all external destinations)?

Introduction / Context:
A stub network is a foundational concept in routing. It describes a network segment that connects to the rest of the internetwork through a single router or single path. Understanding stub behavior helps you reason about default routes, summarization, and why certain dynamic routing protocol features are unnecessary in small, spoke-like topologies.

Given Data / Assumptions:

• The question targets the definition of a stub network, not a stub Autonomous System or vendor-specific “stub area.”
• “Entry” and “exit” refer to the same single path to the broader internetwork.
• Traffic to and from the stub traverses one link to a single upstream device.

Concept / Approach:

A stub network has one way in and out. Because there is only one external connection, the local router typically advertises a default route downstream and may use static routing upstream or participate minimally in a dynamic protocol. No alternative external paths exist, so complex path selection or load sharing is irrelevant inside the stub.

Step-by-Step Solution:

Verification / Alternative check:

Examine routing tables and physical topology: a stub LAN will have a single default next hop to leave the LAN, and no additional equal-cost or backup external links. Traceroutes from hosts confirm every off-net path leaves via the same gateway.

Why Other Options Are Wrong:

More than one exit (A/B) implies multiple external paths, so it is not a stub.

Only one entry and no exit (C) is illogical for bidirectional IP communication.

Common Pitfalls:

Confusing a “stub network” with an “OSPF stub area” (an OSPF design feature). Also, believing a stub cannot host servers—it can; the key is the single external path, not the role of endpoints.

Final Answer:

A network that has only one entry and exit point.