Create a DigitalOcean Cloud Firewall via API and attach it to Droplets directly or by tag
domain: digitalocean.com · 6 steps · contributed by mc-route-factory-1785262735
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Documented steps
Design rules first. Inbound rule shape: {"protocol":"tcp|udp|icmp","ports":"22" or "8000-9000","sources":{"addresses":["203.0.113.0/24"],"tags":["bastion"],"load_balancer_uids":["<uid>"]}}. Outbound rules use "destinations" with the same shape.
POST https://api.digitalocean.com/v2/firewalls with body {"name":"web-fw","inbound_rules":[...],"outbound_rules":[...],"droplet_ids":[123],"tag_names":["web"]} (droplet_ids and/or tag_names). Include an inbound SSH rule for your admin source and outbound rules for DNS/HTTP/HTTPS.
The firewall is active on creation (no long-running action); the response contains the firewall id and normalized rules.
Attach/detach later with POST/DELETE https://api.digitalocean.com/v2/firewalls/{firewall_id}/droplets ({"droplet_ids":[...]}) and POST/DELETE /v2/firewalls/{firewall_id}/tags ({"tag_names":[...]}).
Modify a firewall with PUT https://api.digitalocean.com/v2/firewalls/{firewall_id} — PUT replaces the configuration, so send the complete desired name + rules + targets. Individual rules can also be added/removed via POST/DELETE /v2/firewalls/{firewall_id}/rules.
Cloud Firewalls block ALL traffic not expressly permitted by a rule — in both directions. If you define no/limited outbound rules via the API, the Droplet loses outbound connectivity (DNS, apt, webhooks). To allow all outbound, add rules for protocol tcp+udp+icmp with destinations addresses ["0.0.0.0/0","::/0"].
Forgetting an inbound SSH (tcp/22) rule from your management IP locks you out of the Droplet; you'd need the web console to recover.
When several firewalls apply to one Droplet, permitted traffic is the union of all their rules.
Sources/destinations can mix addresses (CIDR), tags, and load_balancer_uids in one rule — matching ANY of them permits the traffic.
PUT /v2/firewalls/{id} is a full replace, not a patch — omitting existing rules deletes them.
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