Firewall rule helper with CIDR validation, Linux commands, edge snippets and rollback notes
Draft firewall rules for common defensive tasks, validate IPv4 CIDR ranges, review port exposure, generate UFW, iptables, nftables, firewalld, Nginx and Cloudflare-style snippets, and copy a change report before touching a live server.
These are defensive drafts. Test on staging or a maintenance window, keep console access available, and adapt syntax to your distribution, cloud firewall and hosting panel.
A firewall rule helper should help you think before you paste
Firewall syntax is easy to copy and easy to get wrong. A single broad allow rule can expose SSH, a database or a dashboard to the internet. A single broad deny rule can lock you out of a server you manage remotely. Good firewall work starts with a plain question: who should reach which service, from where, over which protocol, and how will you reverse the change if the result is not what you expected?
This firewall rule helper is built around that workflow. It validates the source IP or CIDR, expands port ranges into a readable service matrix, generates command drafts for common Linux firewalls, gives Nginx and Cloudflare-style edge examples, flags risky exposure patterns and prepares rollback notes. It does not apply rules for you. That delay is intentional because production firewall changes deserve review.
How to use the generated rules safely
Start with the smallest source range that solves the problem. For SSH, that usually means your current public IP, a VPN range or a management subnet, not the entire internet. For public web traffic, ports 80 and 443 can normally be open, but admin panels, databases, caches, Elasticsearch, RDP and monitoring dashboards should be restricted. If you are behind a cloud provider firewall, configure both the provider layer and the server layer deliberately so they do not contradict each other.
- Keep a second session open before changing SSH access.
- Apply allow rules first when a later deny rule could affect remote admin access.
- Use CIDR carefully; a /32 is one IPv4 address, while /0 means everyone.
- Document rollback before running commands on a live host.
- Retest from outside with a port checker after the change.
Common firewall examples
An SSH admin rule usually allows port 22 from one trusted source and denies everyone else at the network boundary. A web server normally allows ports 80 and 443 publicly, while WordPress admin protection is better handled with authentication, rate limits and application controls. A database rule should almost never expose 3306, 5432, 6379 or 9200 to the open internet. Emergency blocking can be useful, but broad blocks should be reviewed so they do not affect proxies, uptime monitors or payment callbacks.
Common questions
Can I paste these commands directly on my server?
Treat them as drafts. Check interface names, IPv6 support, cloud firewall policy, existing rule order and persistence settings first.
Which firewall tool should I use?
Use the tool your server already manages. On Ubuntu that is often UFW. On newer distributions nftables may be the real backend. Avoid mixing tools without understanding the active ruleset.
Why include rollback commands?
Because the best time to plan a rollback is before the change. It is especially important for SSH and remote admin rules.
What is the difference between ufw, iptables and nftables?
nftables is the modern Linux packet filter; iptables is the older interface now backed by nftables; ufw is a friendly front-end over them. ufw for simple hosts, nftables for full control.
What is a sensible default firewall policy?
Default-deny inbound, allow established and related connections, allow only the specific ports you need (such as SSH and HTTPS), and allow all outbound unless you have a reason to restrict it.
Do I need to persist firewall rules?
Yes. Rules added at runtime vanish on reboot unless saved. Use the distro mechanism (ufw enable, netfilter-persistent, or an nftables config file) so they reload at boot.
