Incident response guides
Signals to check first, command examples, common misdiagnoses, and recovery order. After reading, practice on a problem about the same failure.
When firewalld looks open but connections keep getting blockedAn InfraTree guide that lays out the first signals to check, the CLI verification order, common misdiagnoses, and a safe recovery path when a port rule appears to exist but the connection fails because of zone, runtime/permanent drift, source binding, or an upstream firewall.Network3 min readHow to separate timeout and connection refused by network pathAn InfraTree guide that lays out the first signals to check, the CLI verification order, common misdiagnoses, and a safe recovery path when DNS, route, firewall, proxy, and listener states all look like the same connection failure.Network3 min readWhen DNS changed but some clients still hit the old backendAn InfraTree guide that lays out the first signals to check, the CLI verification order, common misdiagnoses, and a safe recovery path when the DNS record is updated but resolver cache, HTTP/2 keepalive, or client pools hold on to the old target.Network3 min readWhy only one VLAN works and the rest fail on a native VLAN mismatchA search-oriented symptom guide covering native VLAN mismatch, trunk configuration drift, partial inter-VLAN failures, and Router-on-a-Stick confusion.Network3 min readA checklist for when OSPF adjacency won't formA search-oriented checklist guide covering OSPF neighbor down, stuck adjacency, route loss after failover, and partial path drift.Network3 min readHow to distinguish Router-on-a-Stick from SVI in practiceA search-oriented guide comparing Router-on-a-Stick and SVI by inter-VLAN routing, gateway location, and which point to trust in the logs during an incident.Network2 min read