Testing firewall rules continuously with Zabbix: what should — and shouldn't — be reachable
Network segmentation looks great on the diagram: the DMZ can’t reach the database VLAN, office workstations can’t reach server management interfaces, backups are reachable only from the backup server. Then a year passes. Someone adds a temporary “any-any” rule to debug an issue. A firewall migration converts policies slightly differently. A new VLAN is created by copying an old one.
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