---
title: iptables Command Cheatsheet
description: "# The Linux `iptables` Command The Linux `iptables` command is a powerful tool for configuring and managing firewall rules. It allows users to define rules for incoming and outgoing traffic, set policies for handling packets, and ensure network security. This…"
url: "https://www.relianoid.com/resources/knowledge-base/misc/iptables-command-cheatsheet/"
updated: "2025-05-27"
category: Misc
---

# iptables Command Cheatsheet

# The Linux `iptables` Command

The Linux `iptables` command is a powerful tool for configuring and managing firewall rules. It allows users to define rules for incoming and outgoing traffic, set policies for handling packets, and ensure network security. This guide provides a complete overview of `iptables`, with examples to illustrate key uses.

## Key Usage and Syntax of the `iptables` Command

The `iptables` command follows a general syntax structure:

`iptables [OPTIONS] COMMAND CHAIN RULE`

- **OPTIONS** modify the behavior of `iptables`, like `-v` for verbose output.
- **COMMAND** specifies the action, such as `-A` to append a rule or `-D` to delete a rule.
- **CHAIN** is the target chain where the rule will be applied (e.g., `INPUT`, `OUTPUT`, or `FORWARD`).
- **RULE** defines criteria like source, destination, protocol, etc.

## `iptables` Command Cheatsheet Table

| Command | Description |
| --- | --- |
| `iptables -L` | List all rules in the default filter table |
| `iptables -A INPUT -s <IP> -j DROP` | Block all incoming traffic from a specific IP |
| `iptables -A OUTPUT -p tcp --dport 80 -j ACCEPT` | Allow outgoing traffic on port 80 (HTTP) |
| `iptables -D INPUT -s <IP> -j DROP` | Delete a specific rule that blocks an IP |
| `iptables -F` | Flush all rules in the filter table |
| `iptables -P INPUT DROP` | Set default policy for INPUT chain to DROP |

## Commonly Used Chains in `iptables`

- **INPUT**: Handles incoming connections to the host.
- **OUTPUT**: Manages outgoing connections from the host.
- **FORWARD**: Manages packets that are routed through the host.

## Examples of `iptables` Commands

### Listing All Rules

`iptables -L`

This command lists all the rules in the current `iptables` configuration, along with details of each rule.

```
Chain INPUT (policy ACCEPT)
target     prot opt source               destination
DROP       all  --  192.168.1.100        anywhere

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination
```

### Allowing Specific Traffic

To allow incoming traffic on a specific port, such as SSH (port 22):

`iptables -A INPUT -p tcp --dport 22 -j ACCEPT`

This command appends a rule allowing TCP traffic on port 22 in the INPUT chain.

### Blocking Traffic from an IP Address

`iptables -A INPUT -s 192.168.1.100 -j DROP`

This command blocks all incoming traffic from the specified IP address.

### Flushing All Rules

`iptables -F`

Use this command to flush (remove) all rules in the default filter table, resetting all chains.

### Setting Default Policies

Set a default policy to drop incoming packets:

`iptables -P INPUT DROP`

This command sets the default policy for the INPUT chain to `DROP`, blocking any traffic not explicitly allowed by a rule.

### Saving and Restoring `iptables` Rules

After setting up `iptables` rules, save them to persist across reboots.

- Save: `iptables-save > /etc/iptables/rules.v4`
- Restore: `iptables-restore < /etc/iptables/rules.v4`

## Summary

The `iptables` command provides granular control over packet filtering and firewall management on Linux. With it, users can define rules for different types of network traffic, block or allow specific IPs, and set default policies for added security.

### 📄 Download this document in PDF format