After a VLAN migration, a VIP answers from some subnets and times out from others. Someone shouts duplicate IP. Prove it.

Duplicate-IP claims need evidence, and one command provides it. Then the real skill: telling a genuine two-owner clash apart from ARP flux, because the fixes could not be more different.

Updated Sep 2026 · Grounded in researched DevOps, SRE and platform engineering interview loops, written to a senior-engineer editorial bar, and never padded to hit a word count.

Duplicate-IP claims need evidence, and one command provides it. Then the real skill: telling a genuine two-owner clash apart from ARP flux, because the fixes could not be more different.

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