Network Devices and Their Functions

In a computer room or data center, various devices are present (servers, components, etc.)
  - Each device performs a specific function within the network.
  - Devices can be standalone or combined into one device.
  - Example: A home wireless router combines routing, switching, access point, and security software.

Routers
  - Used to communicate from one IP subnet to another.
  - Function: Makes forwarding decisions based on the destination IP address in a packet.
  - Routers contain a routing table to determine where to send traffic.
  - After evaluating the destination IP address, traffic is sent out through the appropriate interface.
  - Can connect different types of networks (e.g., Ethernet to wireless, fiber to copper).
  - Routers operate at OSI Layer 3 and some combine routing and switching functions (layer 3 switches).

Switches
  - Connect end devices and forward traffic based on MAC addresses.
  - Operate quickly by executing switching internally via hardware (often an Application-Specific Integrated Circuit, or ASIC).
  - A typical workgroup switch may have 24 or 48 ports while core switches can have hundreds of ports.
  - Power over Ethernet (PoE): Some switches provide both data and power over the same Ethernet wires, enabling connection and powering of devices like phones and wireless access points.

Unmanaged Switches
  - Plug-and-play devices that are simple with no configuration options and no management functionality.
  - All ports function as a single VLAN; cannot differentiate between VLANs.
  - No logging or SNMP capabilities; offers a lower price point.
Managed Switches
  - More complex devices that can be managed remotely and configured for advanced settings.
  - Support VLANs, prioritize traffic, and provide redundancy.
  - Can perform port mirroring, allowing traffic monitoring by redirecting traffic to a monitoring device.

Access Points (APs)
  - Enables wireless devices to connect to wired networks.
  - A WLAN access point refers to a bridging device between a wired and wireless network.
  - Access points evaluate frames based on destination MAC addresses, similar to switches, without IP address translation.

Used to manage cabling in networks, connecting individual desks to a central closet using Ethernet cables.
  - Termination onto a punch-down block simplifies cable management.
  - Allows flexibility for changes in network connections without altering the cabling between desks and the patch panel.
  - RJ45 connectors typically used on the patch panel side for connecting to network switches.

Traditional Firewalls
- Control traffic based on TCP or UDP port numbers using access lists.
- Accept or deny traffic according to predefined rules.
Next-Generation Firewalls
  - Operate at a deeper level by recognizing applications instead of just port numbers.
  - Can allow web traffic while blocking remote access software.
  - Functions as a VPN concentrator for both site-to-site and remote access VPNs.
  - May act as a proxy to monitor and filter the traffic that passes through them.
  - Commonly integrated with routing functionality, managing multiple networks.

Power over Ethernet (PoE)
  - Saves installation complexity by combining power and data via Ethernet cabling.
  - Devices powered by PoE include phones, access points, etc.
  - Built into many switches or can be provided via injectors.
  - Endspan PoE: Power supplied by the switch.
  - Midspan PoE: Power supplied by an injector.

PoE: 15.4 watts, max 350 milliamps
PoE+: 25.5 watts, max 600 milliamps (for higher demand devices)
PoE++: 51 watts (600 milliamps) or 71.3 watts (960 milliamps) for very high demand devices like laptop charging.
Compatibility: PoE standards are downward compatible but not upwards.

Cable Modem
- Connects using coax for broadband connections, referred to as DOCSIS (Data Over Cable Service Interface Specification).
- Common speeds are 1 Gbps and higher.
DSL (Digital Subscriber Line)
  - Provides internet connection using telephone lines.
  - Typically offers 200 Mbps downstream and 20 Mbps upstream, distance-dependent.
  - Connection limited to approximately 10,000 feet from the central office.
Fiber Optic Connections
  - Users may connect using an Optical Network Terminal (ONT) that converts fiber to copper for standard network use.
  - The ONT is the demarcation point between user responsibility and service provider responsibility.
  - Contains connections for RJ11 (voice), RJ45 (data), and possibly an F-connector for video.

NIC: Connects devices to the Ethernet network, built into system boards or as expansion cards.
  - Supports various types of Ethernet connections (100 Mbps, Gigabit, Fiber).
  - Each NIC has its own Media Access Control address (MAC address) to uniquely identify its device on the network.
  - Expanding functionality for additional Ethernet connections can be achieved through separate NICs.