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2026-07-17palo-altopan-oslayer2vlanzonestcpdumptroubleshootingpost-mortem

The Switch Was the Firewall

My CI runner could not SSH to my production host. Same VLAN, both up, both healthy, and every packet between them disappeared. No firewall log. No error. No RST. Just silence.

The Ghost Was a Cable

I built a backup vault for my lab: a small Rocky Linux container on the most restricted VLAN I have, the database zone. Fresh container, correct IP, correct gateway. First test:

Giving the Lab a Pager

In the previous post, a server died and stayed dead for five weeks before I noticed. The autopsy taught me the lesson every ops book repeats and every homelab ignores: a system nobody watches fails in silence.