2.2a - Network Devices: Professor Messer

Exam Objectives

Routers

• Routes/forwards traffic between different IP subnets

• If inside a switch, sometimes called “layer 3 switches”

• May connect different network types, like LAN, WAN or fiber networks

Switches

• Forwards traffic based on data link/MAC addresses (layer 2 of the OSI model)

• Uses an application-specific integrated circuit (ASIC) that provides high throughput (this is included in the switch hardware, typically).

• Core of an enterprise network, and may provide Power over Ethernet (PoE) capabilities

• Managed: Switch that provides configuration options, such as:

  • VLANs

  • Traffic prioritization

  • Redundancy support (multiple switches) via Spanning Tree Protocol (STP)

  • Allows port mirroring: Capture traffic on one switch port and copy it to another switch port

  • External management via Simple Network Management Protocol (SNMP)

    

• Unmanaged: Fewer configuration options for switch usage; simple plug-and-play usage.

  • VLAN functionality is limited; all devices connect to the same VLAN.

  • Little integration with SNMP or other network devices; difficult to query network/performance details.

  • Cheap prices: Lower costs compared to managed switches

  

Access points (WAPs)

• NOT A ROUTER: Bridges connectivity from a wired network to a wireless network.

• Makes forwarding decisions based on destination MAC addresses

Patch panel

• Networking device with multiple ports that organize/manage network cables in a central location (typically a wiring closet).

• Patch panels may contain ports/connectors that extend to switches or other networking devices

• To connect a workstation to a different switch, move the cable between the switch and the patch panel port (the green cable in the image).

  

Firewalls

• Filter traffic by IP addresses and port number

• TCP/UDP ports operate at layer 4 of the OSI model - firewalls are often called OSI layer 4 devices

  • If the firewall understands application-level traffic (e.g., HTTP), it is known as a layer 7 OSI device.

• Can also act as an encrypted tunnel - encrypting data sent between two different websites.

• Can act as a proxy for traffic: Receives an internet traffic query(a web search) from a user, then checks the response of that query over the internet (so no traffic is malicious/dangerous), then sends the results of the query to the user.

• Typically acts as a layer 3 OSI device (a router) in SOHO environments, and allows additional traffic forwarding functionality.

Power over Ethernet (PoE)

• Refers to networking devices powered by an already connected ethernet cable - Ethernet cable transfers both data and electrical power to networking devices

  • Injectors: Endspans refer to built-in power, and midspans refer to in-line power injectors.

  • Switch: Some switches support Power over Ethernet (PoE) - this is commonly marked on the switch/switch interfaces

    

  • PoE standards

    Original standard - IEEE 802.3af (2003), 15.4W DC power, currently part of the 802.3 standard

    Enhanced standard - IEEE 802.3at (2009), also known as PoE+, which allows for higher power delivery up to 30 watts.
    Newest standard - IEEE 802.3bt (2018), known as PoE++, which supports even greater power levels, enabling up to 51 watts per port in Type 3 and 71.3 watts per port in Type 4 configurations.

Hub

• Networking device that connects multiple Ethernet devices, making them act as a single network segment.

  • Called “multi-port repeaters” - traffic in one port is repeated to every other port

• Operate at layer 1 of the OSI model

• Only capable of half-duplex (HDX) communication (think of a walkie-talkie - one person can talk at once)

• Outdated devices; replaced by switches

Cable modem

• Uses broadband communication to transmit multiple types of data - video signals for television, phone lines for voice communication, and internet data.

• Allows speeds of up to 1Gbps, though this may vary according to service providers.

Digital subscriber line (DSL)

• Uses telephone connections

• Technically called ASDL (Asymmetric Digital Subscriber Line)

  • Called asymmetric because the download speed is much faster than the upload speed (asymmetric)

• Uses telephone signals to provide both telephone and internet connectivity

• Typical speeds: 52Mbps download (downstream) and 16Mbps upload (upstream)

• ~10,000 ft range limitation from central office (CO) - a building in the neighborhood that serves local phone lines.

• May have faster speeds if closer to the CO

Optical network terminal (ONT)

• Uses fiber/optical connections

• Connects an ISP fiber network and converts optical signals to copper Ethernet that can be used for internet connectivity.

• Separates/delineates traffic to multiple points - your network (past the demarcation point), and the ISP (before the demarcation point).

Network interface card (NIC)

• Fundamental networking component that allows internet/Ethernet connectivity to any endpoint (computers, printers, servers, phones, routers, etc.)

  • Any device with network connection capability has a NIC

• Can be specific to a network type (e.g., Ethernet, wireless)

• Often built into the motherboard, but can be added as an expansion card.

• Many options - single-/multi-port, copper, fiber