Network Devices - Routers, Switches, Firewalls, IDS/IPS

Network Devices

Understand the functions of routers, switches, firewalls, and IDS/IPS in network infrastructure.

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Router

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Switch

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Firewall

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IDS/IPS

Routers

Routers are networking devices that forward data packets between computer networks. They perform the traffic directing functions on the Internet and are essential for connecting different networks together.

Routers connect different networks and direct traffic between them

Network A

Network B

Key Functions

• Path determination using routing tables
• Packet forwarding between networks
• Network address translation (NAT)
• Quality of Service (QoS) management
• Connecting LANs to WANs or the Internet

Types of Routers

• Core routers (backbone of the Internet)
• Edge routers (connect to other networks)
• Branch routers (connect remote offices)
• Wireless routers (provide Wi-Fi connectivity)
• Virtual routers (software-based routing)

Did you know? Routers use routing protocols like OSPF, EIGRP, and BGP to exchange information and determine the best paths for network traffic.

Switches

Network switches are devices that connect devices together on a computer network by using packet switching to receive and forward data to the destination device. They operate at the data link layer (Layer 2) of the OSI model.

Switches connect devices within a local network

Key Functions

• Frame forwarding based on MAC addresses
• Learning MAC addresses of connected devices
• Preventing collisions in Ethernet networks
• Creating separate collision domains
• Supporting full-duplex communication

Types of Switches

• Unmanaged switches (basic plug-and-play)
• Managed switches (configurable features)
• Smart switches (limited management)
• Layer 3 switches (routing capabilities)
• PoE switches (Power over Ethernet)

Did you know? Switches maintain a MAC address table to map MAC addresses to specific ports, enabling efficient frame forwarding.

Firewalls

A firewall is a network security device that monitors and filters incoming and outgoing network traffic based on an organization's previously established security policies. Firewalls act as a barrier between secure internal networks and untrusted external networks like the Internet.

Firewalls protect networks by controlling incoming and outgoing traffic

Trusted Network

Untrusted Network

Key Functions

• Packet filtering based on rules
• Stateful inspection of connections
• Application-level gateway services
• VPN support for secure remote access
• Intrusion prevention capabilities

Types of Firewalls

• Packet-filtering firewalls (basic filtering)
• Stateful inspection firewalls (track connections)
• Next-generation firewalls (advanced features)
• Proxy firewalls (application-level filtering)
• Cloud-based firewalls (as-a-service)

Important: Firewalls must be regularly updated with the latest security rules and threat intelligence to effectively protect against evolving cyber threats.

IDS/IPS Systems

Intrusion Detection Systems (IDS) and Intrusion Prevention Systems (IPS) are security appliances that monitor network traffic for suspicious activity and known threats. While IDS alerts administrators of potential threats, IPS takes action to block detected threats.

IDS/IPS systems detect and prevent network intrusions

Network Segment

IDS

IPS

Protected Network

IDS Functions

• Monitoring network traffic for suspicious patterns
• Detecting known attack signatures
• Identifying policy violations
• Generating alerts for security incidents
• Providing forensic data for analysis

IPS Functions

• Actively blocking detected threats
• Dropping malicious packets
• Resetting connections when attacks are detected
• Applying security patches automatically
• Preventing data exfiltration

Did you know? IDS/IPS systems can be network-based (NIDS/NIPS) monitoring entire networks or host-based (HIDS/HIPS) protecting individual devices.

Device Comparison

The following table compares the key characteristics of routers, switches, firewalls, and IDS/IPS systems:

Feature	Router	Switch	Firewall	IDS/IPS
OSI Layer	Layer 3 (Network)	Layer 2 (Data Link)	Layers 3-7	Layers 3-7
Primary Function	Connect networks	Connect devices	Filter traffic	Detect/Prevent threats
Decision Basis	IP addresses	MAC addresses	Security rules	Threat signatures
Security Focus	Low	Low	High	Very High
Typical Placement	Network edge	Within networks	Network perimeter	Network perimeter/segments