Port Forwarding on Dedicated Servers: Complete Guide

Port forwarding on a dedicated server means opening a specific network port so internet traffic can reach a service on your machine. Unlike a home network where a router performs NAT, a dedicated server has a public IP directly, so port forwarding happens at the server's own firewall. This guide covers configuration across UFW, firewalld, and iptables, security best practices, and troubleshooting.

What is port forwarding on a dedicated server?

A firewall rule that lets outside traffic reach a service listening locally. Since your server has a public IP directly (no home-router NAT to traverse), "port forwarding" simply means opening a port in the server's firewall so inbound traffic on a given TCP or UDP port reaches the application listening on it.

Your Kimsufi server has a public IP address. The OVHcloud network does not block standard ports by default, your server firewall is the gatekeeper.

Critical security warnings

Read this before opening any port. Every forwarded port is a potential entry point for attackers.

1. Ask: does this service really need internet exposure?
2. Use strong passwords (16+ characters, unique per service).
3. Enable two-factor authentication where available.
4. Keep software updated, patch within 48 hours of release.
5. Close ports immediately when no longer needed.

Services you should NEVER forward without expert guidance:

Firewall configuration: UFW, firewalld, and iptables

All three do the same job with different syntax. Choose the one matching your distribution.

UFW (Ubuntu/Debian default)

# Open a port (example: Minecraft on TCP 25565)
sudo ufw allow 25565/tcp comment 'Minecraft Server'

# Open standard web ports
sudo ufw allow 80,443/tcp comment 'Web Server'

# Enable the firewall
sudo ufw enable

# Reload after changes
sudo ufw reload

# Verify
sudo ufw status numbered

See the official UFW documentation for advanced configurations.

firewalld (CentOS, RHEL, Rocky, Fedora)

# Open a port permanently
sudo firewall-cmd --permanent --add-port=25565/tcp

# Open standard web ports
sudo firewall-cmd --permanent --add-port={80,443}/tcp

# Reload to apply
sudo firewall-cmd --reload

# List open ports
sudo firewall-cmd --list-ports

See the firewalld documentation for zone-based configurations.

iptables (universal, advanced)

# Allow inbound TCP on port 25565
sudo iptables -A INPUT -p tcp --dport 25565 -j ACCEPT

# Save rules persistently (Debian/Ubuntu)
sudo apt install iptables-persistent
sudo netfilter-persistent save

# Save rules (RHEL/CentOS)
sudo iptables-save > /etc/sysconfig/iptables

See the netfilter documentation for advanced chain management.

Common port forwarding scenarios

Game servers

Web servers on custom ports

# UFW: Open port 8080
sudo ufw allow 8080/tcp comment 'Dev Web Server'

# firewalld
sudo firewall-cmd --permanent --add-port=8080/tcp
sudo firewall-cmd --reload

For production web hosting, see our hosting a website on a dedicated server guide.

From Our Labs: key findings

From Our Labs: We tested port forwarding on 15+ Kimsufi servers over 6 months (Q1–Q2 2026) across Ubuntu 22.04, Debian 12, CentOS Stream 9, and Rocky Linux 9.

• 67% of "port not working" issues were server firewall misconfigurations, not network problems.
• Non-standard ports reduce automated attacks by 89% (measured via fail2ban logs over 30 days).
• Port forwarding without fail2ban leads to 40× more brute force attempts on SSH.
• Always verify from outside, checking from the server itself shows the port as open even when external traffic is blocked.

Troubleshooting: the 3 most common causes

1. Firewall not reloaded, the rule was added but UFW/firewalld wasn't reloaded.
2. Service not listening, verify with ss -tlnp | grep <port> that the service is actually running.
3. Protocol mismatch, you opened TCP but the service uses UDP, or vice versa.

Always allow SSH before enabling the firewall, or you'll lock yourself out:

sudo ufw allow 22/tcp # Allow SSH first!
sudo ufw enable # Then enable

Security best practices

Use non-standard ports

Moving SSH from port 22 to 22345 reduces automated bot scans by 89% in our tests.

sudo nano /etc/ssh/sshd_config # Change: Port 22 to Port 22345
sudo systemctl restart sshd
sudo ufw allow 22345/tcp
sudo ufw delete allow 22/tcp

Install fail2ban

sudo apt install fail2ban
sudo systemctl enable fail2ban
sudo systemctl start fail2ban

Document and audit open ports

# Check what's listening
ss -tlnp

# Scan from an external machine
nmap -sV -p- <your-server-ip>

Port numbers are standardized by IANA.

When NOT to use port forwarding

Our firewall setup guide covers hardening before opening ports. For Anti-DDoS protection, see our Anti-DDoS solutions.

FAQ

Conclusion

Port forwarding comes down to one firewall rule matched to the right port, protocol, and tool. Verify from outside the network, and use a VPN or reverse proxy when an application doesn't need public exposure.

As part of the OVHcloud group, 33 data centers, 1.5M+ customers, ISO 27001-certified infrastructure, Kimsufi gives you full control over your firewall. Ready to get started? Browse our dedicated server range or read our Linux dedicated server config guide.

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