On classic 10 Mbps Ethernet (IEEE 802.3) using the 5-4-3 rule, what is the maximum number of repeaters allowed between any two nodes on a collision domain?

Introduction / Context:
Early shared-media Ethernet imposed physical-layer limits to ensure that collision detection worked reliably and that signals maintained integrity over distance. The well-known “5-4-3” guideline constrained the number of segments and repeaters that could exist between any two stations. This question asks for the maximum number of repeaters permitted between hosts on a single collision domain under that rule.

Given Data / Assumptions:

• Classic 10 Mbps Ethernet (10BASE5/10BASE2/10BASE-T in shared modes).
• Shared collision domain with repeaters (hubs) extending reach.
• Use of the 5-4-3 rule (five segments, four repeaters, three populated segments).

Concept / Approach:
The 5-4-3 rule states: between any two stations, you may have at most five segments connected by four repeaters, and of those segments no more than three may be populated (have active hosts). Limiting repeaters controls end-to-end propagation delay so that collisions are detected within a slot time, preserving CSMA/CD's assumptions. Therefore, the answer is four repeaters maximum between two nodes in the collision domain.

Step-by-Step Solution:

Verification / Alternative check:
Ethernet design texts and vendor deployment guides for coax and hub-based topologies reiterate the 5-4-3 rule as the practical limit for 10 Mbps shared Ethernet, aligning with the slot time and propagation constraints of CSMA/CD.

Why Other Options Are Wrong:

• Five / Six: exceed the repeater limit; would break timing budgets.
• Two / Three: stricter than necessary; acceptable but not the maximum permitted by the rule.

Common Pitfalls:
Misremembering which number corresponds to repeaters vs. segments; applying the rule to switched, full-duplex Ethernet (it does not apply there); assuming the same limits for Fast/Gigabit Ethernet, which use different constraints.

Final Answer:
Four.