Network Topology Concepts

The Access Layer

• Controls user and workgroup access to internetwork resources and handles remote service traffic.

Two-Tier, Spine-Leaf Architecture

• Uses high-throughput, low-latency, and port-dense spine switches with direct high-speed connections to each leaf switch.
• Leaf switches have increased capabilities, including 40, 100, or 300Gbps uplinks to each spine switch.

Advantages of Two-Tier, Spine-Leaf Architecture

• Resiliency: Each leaf switch connects to every spine switch, enabling concurrent use of uplinks.
• Latency: Maximum of 2 hops for any East-West packet flows, providing ultra-low latency.
• Performance: True active-active uplinks enable traffic to flow over the least congested high-speed links.
• Scalability: Ability to increase leaf switch quantity and add spine switches as needed.
• Adaptability: Multiple spine-leaf networks can be connected and managed from a single pane of glass.

Cloud and Premises

• Clouds On-premises: Infrastructure, services, and management are within the business on their own hardware and servers.
• Client: A computer or program that requests information from a server.
• Server: A computer or program that provides services or information to clients.

Network Fundamentals

• Network Operating System (NOS): The operating system running on servers.
• Connectivity Device: Any device that connects cable segments, connects two or more small networks, or divides a large network.
• Local-Area Network (LAN): A network confined to a small geographic area.
• Wide-Area Network (WAN): Interconnects LANs using leased carrier lines or satellite technology.

Network Characteristics

• Cost: The general cost of network components, installation, and maintenance.
• Physical Topology: A network's physical shape.
• Logical Topology: The path that data takes from one computer to another.

WAN and SDWAN

• WAN: A network that uses various links to connect smaller metropolitan and campus networks.
• Software-Defined Wide Area Network (SDWAN): A virtual WAN architecture that securely connects users to applications.

Networking Fundamentals

• Network Interface Card (NIC): Connects a computer to a LAN.
• Medium: The physical transport used to carry data, such as a cable.
• Protocol: A set of communication rules used by computer or network devices.
• Cisco IOS Software: The most widely deployed network system software.

Network Topology

• Defines how computers, printers, and network devices are connected.
• Physical Topology: Defines the physical components of the network.
• Logical Topology: Defines the data path of the network.
• Bus Topology: Connects all devices using a single cable.
• Star Topology: The most commonly used physical topology in Ethernet LAN.
• Ring Topology: Hosts are connected in the form of a ring or circle.
• Full Mesh Topology: Connects all devices to each other for redundancy and fault tolerance.

Network Architecture

• 3 Tier Architecture: Consists of the Core Layer, Distribution Layer, and Access Layer.
• Core Layer: The core of the network, responsible for transporting large amounts of traffic.
• Distribution Layer: The communication point between the access layer and the core.
• Security: Defines how secure the network and network data are.
• Availability: The measure of the likelihood that the network will be available for use when required.
• Scalability: How well the network can accommodate more users and more data.
• Reliability: The dependability of the devices that make up the network.

Classes of Attacks

• Passive: Attacks that capture and monitor unprotected communication and capture passwords.
• Active: Attacks that actively try to break or bypass security devices.
• Close-in: Attacks attempted by an individual in close physical proximity to networks or facilities.
• Insider: Attacks that occur from authorized users inside a network.
• Distribution: Attacks that focus on malicious changes to hardware or software during distribution.
• Access Attacks: Exploit known web services, databases, operating systems, and authentication services.
• Examples of Access Attacks: Password attacks, Port redirection, Man-in-the-middle attacks, Buffer overflow.