How it works
A network that works today has to keep working as it grows. Redundancy removes single points of failure, monitoring provides warning, and capacity planning anticipates load. Newer addressing exists because the older space could not grow indefinitely.
Identify the single point whose failure would take everything down, and say what would have to exist for it not to.
Common error
Redundancy that shares a failure path is not redundancy. Two links through the same conduit fail together.
Worked example
Evaluate a redundancy proposal and newer addressing.
Evidence
Primary uplink: conduit A
Backup uplink: conduit A
Addressing growth: additional device groups expectedTwo uplinks in one conduit share a physical failure mode. Consider a genuinely diverse path and appropriate failover testing. IPv6 provides a much larger address space than IPv4, but larger addresses alone do not provide availability, correct routing, or secure policy.
Exercises
4.6.1
Why can two routers connected to the same failed power strip both become unavailable?
Show solution
They share the power strip as a common dependency. Device duplication alone does not remove the shared failure path; assess power diversity and recovery requirements.
4.6.2
What is the address bit length of IPv4 and IPv6, and why does migrating not eliminate the need for firewall rules?
Show solution
IPv4 uses 32-bit addresses and IPv6 uses 128-bit addresses. Address capacity is separate from authorization; required traffic still needs an explicit, verified security policy.