Question 520
During a post-incident review at a research campus, the original problem was: An administrator copies a source NAT rule above a more specific exception, causing sensitive finance flows to leave through the wrong public IP. Which preventive practice most directly addresses its cause?
Explanation
Correct Answer
Run NAT shadowing analysis after inserting new egress rules. This control reduces recurrence of the documented mechanism: NAT rules evaluate by order, so an early broad rule can mask a later narrow one. It creates a repeatable check around the needed response: Move the specific translation above the general rule and scope both appropriately.
Incorrect Answers
Verify each required IP family separately in NAT acceptance tests. That safeguard addresses another potential failure: An engineer creates an IPv4 source NAT policy for an IPv6-only service path and assumes the same rule will translate both address families. It is not the most targeted recurring control for the described cause: NAT rules evaluate by order, so an early broad rule can mask a later narrow one.
Capture representative session path and NAT rule matches before promotion. That safeguard addresses another potential failure: A static source translation is created for a server farm, but egress traffic follows an unexpected route and misses the intended NAT rule. It is not the most targeted recurring control for the described cause: NAT rules evaluate by order, so an early broad rule can mask a later narrow one.
Test inside and outside access to hosted public services before cutover. That safeguard addresses another potential failure: A remote branch allows internal clients to access a web service via its public VIP, but hairpin requests fail because required U-turn NAT is absent. It is not the most targeted recurring control for the described cause: NAT rules evaluate by order, so an early broad rule can mask a later narrow one.