Configure a Firewall with Firewalld for Testnet Nodes

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Running a coins validator nodes or any blockchain nodes are always need require port configuration to secure the server from various outside threats.

there are many software that can be used to perform port management, but here I will discuss only firewalld,

Firewalld is frontend controller for nftables (or its older counterpart, iptables) used to implement persistent network traffic rules. It provides command line and graphical interfaces and is available in the repositories of most Linux distributions.

While firewalld is a frontend for nftables/iptables and allows easier management of firewall rules, it is not a direct replacement for these utilities. Using nftables directly may provide you with more control. When using firewalld, its recommended to use firewall-cmd commands (instead of nftables or iptables commands) to interface directly with firewalld.

• Installing Firewalld (Ubuntu & Debian)

  • sudo apt update && sudo apt install firewalld

• Disable Any other firewall configuration software

  • sudo ufw disable

• Managing Firewalld
  • Starting Firewalld

    • sudo systemctl start firewalldsudo systemctl enable firewalld

  • Stop & Disable Firewalld

    • sudo systemctl stop firewalldsudo systemctl disable firewalld

  • Check firewalld status

    • sudo firewall-cmd --state

  • Check firewalld Daemon Status

    • sudo systemctl status firewalld

  • Reload / Restart Firewalld Configuration

    • sudo firewall-cmd --reload

  • Set Default Zone

    • sudo firewall-cmd --set-default-zone=public

  • Open New Port

    • sudo firewall-cmd --zone=public --add-port=YOUR_PORT/tcp --permanent

    • **change the YOUR_PORT to any port you want to open

    • open port 22 example:sudo firewall-cmd --zone=public --add-port=22/tcp --permanent

  • List All Port

    • sudo firewall-cmd --list-all

  • Remove Port

    • sudo firewall-cmd --zone=public --remove-port=YOUR_PORT/tcp --permanent

    • **change the YOUR_PORT to any port you want to remove
  • Forward Port on Same Server

    • sudo firewall-cmd --zone="public" --add-forward-port=port=FROM_PORT:proto=tcp:toport=TO_PORT

    • **Change your FROM_PORT and TO_PORT

The reload command drops all runtime configurations and applies a permanent configuration. Because firewalld manages the ruleset dynamically, it won’t break an existing connection and session.

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