## Routers: Configuration Guide

A router is a device that connects multiple computer networks, such as a home network to the internet or different office networks to a central one. This page will explain how they work, where they're used, and any potential configuration errors that are worth avoiding.

### What are Routers?

Routers operate at Layer 3 of the OSI Model, often called the "routing" layer because it it this layer that routers use to forward traffic, looking at specific IP addresses in order to determine where next to traverse the network.

### How Routers Work

- Receive and inspect data packets
- Assign local IP addresses to connected devices (via DHCP)
- Determine the most efficient path for packets to reach their destination
- Act as a traffic controller between internal and external networks
- Provide basic security using NAT and built-in firewall features

### Common Router Uses

- Connecting multiple devices to a single internet connection
- Creating and managing local networks (LANs)
- Providing wired and Wi-Fi access
- Segmenting networks for guests and internal users
- Connecting branch offices through VPN tunnels

## ⚠️ Common Router Misconfigurations

Router setup mistakes can expose your entire network to risk. Below are frequent misconfigurations and why they are dangerous.

### 1. Default Credentials

Leaving default usernames and passwords (like `admin/admin`) on router admin accounts is one of the most common and dangerous misconfigurations.

#### Negative Consequences

- Unauthorized access to router settings
- Complete network compromise
- Loss of privacy and data exposure
- Device hijacking for botnets or attacks

### 2. Failure to Update Firmware

Not updating router firmware leaves known vulnerabilities unpatched and exploitable.

#### Negative Consequences

- Exploitation of known vulnerabilities
- Performance and stability issues
- Malware infection of the router
- Overall reduced security posture

### 3. Improper Firewall or Access Control Configuration

Misconfigured firewall rules can either block legitimate traffic or leave critical ports exposed to the internet.

#### Negative Consequences

- Unauthorized network access
- Data breaches and information leakage
- Denial of Service (DoS) conditions
- Operational disruptions for users and services

### 4. Poor Access Controls

Leaving remote management services open, using weak passwords, or not restricting who can reach the admin interface creates an easy entry point for attackers.

#### Negative Consequences

- Unauthorized administrative changes
- Data theft and traffic manipulation
- Network disruption and downtime
- Attackers gaining a foothold for further escalation

### 5. Unused Features Left Enabled

Routers often ship with optional services enabled by default (remote admin, WPS, UPnP, etc.) that are not needed in many environments.

#### Negative Consequences

- Expanded attack surface
- Remote exploits through unnecessary services
- Performance degradation
- Hidden vulnerabilities that are hard to track

### Best Practice Reminder

Always change default credentials, keep firmware updated, disable unused services, and restrict router management access to trusted networks. Test changes in a controlled environment before applying them to production routers.