Network Devices - Lesson 2.5 | CompTIA A+ Core 1 Notes

Introduction to Network Devices

Data centers and computer rooms contain racks of devices like servers, routers, switches, and other components, each performing specific network functions.
Many devices combine multiple functions into a single unit (e.g., a wireless router at home includes a router, switch, access point, and security software).
Understanding individual devices helps in designing and troubleshooting networks effectively.

Routers connect different IP subnets and make forwarding decisions based on the destination IP address in a packet.
They use a routing table to determine the best path for traffic and send it out the appropriate interface.
Operate at OSI Layer 3 (Network Layer).
Some routers also function as Layer 3 switches, combining routing and switching capabilities.
Can connect different network types (e.g., Ethernet to wireless, fiber to copper, or serial networks).

Switches connect end devices and forward traffic based on the destination MAC address.
Operate at OSI Layer 2 (Data Link Layer) but can include Layer 3 functionality (Layer 3 switches).
Use Application-Specific Integrated Circuits (ASICs) for high-speed switching in hardware.
Common port configurations: 24-port or 48-port for workgroup switches; hundreds of ports for core switches.
Support Power over Ethernet (PoE), providing both data and power over the same cable for devices like phones, wireless access points, and laptops.

Unmanaged Switches:
- Plug-and-play with no configuration options.
- No VLAN support; all ports belong to a single broadcast domain.
- No remote management (e.g., no SNMP or logging).
- Lower cost, ideal for simple connectivity needs.
Managed Switches:
- Support advanced configurations like VLANs, traffic prioritization, and redundancy.
- Allow remote management via SNMP, CLI, or web interfaces.
- Support port mirroring for monitoring traffic with tools like protocol analyzers.
- Used in enterprise networks for scalability and security.

Wireless access points (APs) bridge wired and wireless networks without routing or IP translation.
Forward traffic based on MAC addresses, similar to switches.
Common in corporate environments to provide wireless connectivity to end devices.

Simplify cable management by terminating Ethernet cables from desks to a central closet.
One side connects to desks via punch-down blocks (permanent connections).
The other side uses RJ45 connectors for flexible reconfiguration without rewiring.
Allows easy switching between VLANs, switches, or troubleshooting connections.

Traditional Firewalls: Filter traffic based on port numbers (e.g., allow TCP 80 for HTTP, block TCP 22 for SSH).
Next-Generation Firewalls (NGFW): Filter traffic based on applications (e.g., allow web browsing but block remote access tools).
Can act as VPN concentrators for site-to-site or remote access VPNs.
May include proxy functionality to inspect and forward client-server traffic.
Often installed as routers to provide both security and routing between subnets.

Delivers both data and power over Ethernet cables to devices like phones, access points, and cameras.
PoE Standards:
- PoE (802.3af): 15.4W, 350mA (for phones, small devices).
- PoE+ (802.3at): 25.5W, 600mA (for PTZ cameras, larger devices).
- PoE++ (802.3bt): 51W (Type 3) or 71.3W (Type 4), 600mA/960mA (for laptops, high-power devices).
In-Span PoE: Power comes directly from the switch.
Mid-Span PoE: Uses an external PoE injector if the switch lacks PoE support.
Check switch documentation or labels for PoE compatibility.

Cable Modems:
- Use coaxial cables (same as cable TV) to provide broadband internet.
- Follow DOCSIS (Data Over Cable Service Interface Specification) standards.
- Support speeds up to 1 Gbps or higher.
- Common in homes and businesses for high-speed internet.
DSL Modems:
- Use telephone lines to provide digital internet (voice and data simultaneously).
- Throughput depends on distance from the central office (max ~10,000 feet).
- Typical speeds: 200 Mbps downstream, 20 Mbps upstream.
ONT (Optical Network Terminal):
- Converts fiber optic signals to copper (Ethernet/RJ45) for local networks.
- Serves as the demarcation point (boundary between ISP and user responsibility).
- May include RJ11 for VoIP, F-connector for video, and RJ45 for data.

Provide connectivity between devices and the network.
Can be built into motherboards or added via expansion cards.
Types include 100 Mbps, 1 Gbps, or 10 Gbps Ethernet, and fiber optic NICs.
Each interface has a unique MAC address for identification.
Expansion cards allow adding multiple Ethernet ports to a device.