Hierarchical Network Design

• Discrete layers divide the network in hierarchical network design
• Each layer has specific functions related to the overall network.

Access Layer

• Interfaces with end devices like PCs, printers, and IP phones to provide network access
• Connects devices to the network, controlling which are allowed to communicate

Distribution Layer

• Aggregates data from access layer switches before transmission to the core layer
• Routes data towards its final destination

Core Layer

• High-speed backbone of the internetwork
• Critical for interconnectivity between distribution layer devices, must be highly available and redundant

Benefits of Hierarchical Networks

• Scalability: Modular design allows for easy expansion
• Redundancy: Minimizes latency and bandwidth contention
• Performance: Enhanced control through port security and access policies
• Security
• Manageability: Simplified changes across the same layer
• Maintainability

Principles of Hierarchical Network Design

• Network Diameter: The number of switches packets cross impacts latency
• Bandwidth Aggregation: Combines switch port links for higher throughput
• Redundancy: Important in creating a highly available network

Converged Networks

• Include Voice, Video and Data Networks

Voice Networks

• Contain isolated phone lines running to a Private Branch Exchange (PBX) switch
• PBX switches allow phone connectivity to the Public Switched Telephone Network (PSTN)
• Adding a new phone requires running a new line back to the PBX

Videoconferencing

• Equipment is wired separately from voice and data networks
• Videoconferencing data can consume significant bandwidth

Data Networks

• Interconnect workstations and servers, facilitating resource sharing
• Data networks can consume significant data bandwidth

Traffic Flow Analysis

• Process of measuring bandwidth usage and analyzing data for performance tuning
• Used for capacity planning and making hardware improvement decisions
• Done using traffic flow analysis software

User Communities Analysis

• Grouping users based on job functions
• Affects port density and traffic flow

Data Stores

• Include servers, Storage Area Networks (SANs), Network Attached Storage (NAS), and tape backup units

Server-Server Traffic

• Traffic generated between data storage devices on the network

Topology

• A graphical representation of a network infrastructure

Switch Form Factors

• Fixed switches: Pre-configured and cannot be expanded
• Modular switches: Allow adding expansion cards for scalability
• Stackable switches: Interconnected with high-speed backplane cables for redundancy and fault tolerance

Performance Considerations for Switches

• Key factors in switch selection include:
  • Port Density: More ports allow better device connectivity
  • Forwarding Rates: Determines how much data a switch can process
  • Bandwidth Aggregation: Reduces congestion and increases throughput

Link Aggregation

• Technique used to combine multiple network connections
• Designed to increase bandwidth and provide redundancy

Power over Ethernet (PoE)

• Allows a switch to deliver power to a device over existing Ethernet cabling

Access Layer Switch Features

• Port Security: Controls which devices can connect
• VLANs: Separates traffic, improving security and performance
• Port Speed: Supports Fast Ethernet (100 Mbps) or Gigabit Ethernet (1000 Mbps) for efficient data transfer
• PoE (Power over Ethernet): Provides power to devices like IP phones and wireless access points
• Link Aggregation: Combines multiple links for better bandwidth and reliability
• QoS (Quality of Service): Prioritizes traffic for voice, video, and data transmission

Distribution Layer Switch Features

• Inter-VLAN Routing: Allows VLANs to communicate
• Layer 3 Functions: Supports routing for efficient data transfer
• QoS (Quality of Service): Maintains traffic priority across the network
• Redundancy: Uses multiple switches and power supplies to ensure reliability
• Link Aggregation: Supports high-bandwidth connections to the core layer

Core Layer Switch Features

• High Forwarding Rates: Supports large volumes of data traffic
• Link Aggregation: Ensures high bandwidth from distribution switches
• Redundancy: Uses Layer 3 redundancy and hot-swappable hardware for reliability
• QoS (Quality of Service): Prioritizes mission-critical traffic like voice and video

Cisco Catalyst Switches

• Catalyst Express 500: Basic Layer 2 switch for small networks, simple management, supports 20-250 employees
• Catalyst 2960: Supports VLANs, Power over Ethernet (PoE), and Quality of Service (QoS) for better traffic management
• Catalyst 3560: Layer 3 capabilities with advanced security and PoE support, forwarding rates of 32 Gb/s to 128 Gb/s
• Catalyst 3750: Stackable switch, allowing multiple switches to function as a single unit with enhanced performance, supports forwarding rates from 32 Gb/s to 128 Gb
• Catalyst 4500: Forwarding rates up to 136 Gb/, capable of managing traffic at the distribution layer
• Catalyst 4900: Ideal candidates for back-end IP telephony hardware, an access layer switch for data center deployments
• Catalyst 6500: Supporting forwarding rates up to 720 Gb/s, capable of managing traffic at the distribution and core layers

CSMA/CD (Carrier Sense Multiple Access with Collision Detection) Mechanism

• Carrier Sense: Devices listen before transmitting to avoid collisions
• Multi-access: If two devices transmit simultaneously, a collision occurs
• Collision Detection: Devices detect collisions through increased signal amplitude
• Jam Signal and Random Backoff: A jam signal notifies devices of a collision It's followed by a random backoff to avoid repeated collisions

Ethernet Communications

• Unicast: One sender, one receiver (e.g., HTTP, FTP)
• Broadcast: One sender, all recipients (e.g., ARP queries)
• Multicast: One sender, selected recipients (e.g., video conferencing)

Ethernet Frame Structure

• Preamble & Start Frame Delimiter (SFD): Synchronization (8 bytes)
• Destination & Source MAC Address: Identifies recipient and sender (6 bytes each)
• Length/Type: Defines frame length or type (2 bytes)
• Data & Pad: Encapsulated Layer 3 PDU (46-1500 bytes)
• Frame Check Sequence (FCS): Error detection via CRC (4 bytes)

MAC Addressing

• Organizational Unique Identifier (OUI): Identifies the manufacturer
• Vendor Assignment Number: Identifies the specific device

Duplex Settings

• Half Duplex: Unidirectional at a time, requires CSMA/CD, used in older hubs (prone to collisions)
• Full Duplex: Simultaneous transmission and reception, requires full-duplex NICs and switches, no collisions

Network Latency

• Delay in data transmission, influenced by:
  • NIC delay: Time for a network card (NIC) to send and interpret signals
  • Propagation delay: Time for a signal to travel through cables
  • Network device delay: Time spent processing packets in network devices

Network Congestion

• Occurs when excessive data traffic overwhelms the network, due to:
  • More powerful computers sending data at higher speeds
  • Increased network traffic from broadcast messages and remote resource access
  • High-bandwidth applications

LAN Segmentation

• Reduces congestion and increases bandwidth efficiency. Methods include:
  • Switches: Reduce collision domains but not broadcast domains
  • Routers: Create separate broadcast domains, reducing overall traffic
  • VLANs: Logically separate broadcast domains within a single switch network

OSI Layers

• The Open Systems Interconnection (OSI) model includes 7 layers
• Layer 7: Application
• Layer 6: Presentation
• Layer 5: Session
• Layer 4: Transport
• Layer 3: Network
• Layer 2: Data Link
• Layer 1: Physical

Configuration commands

• Switch1# conf t - Enter configuration mode
• Switch1(config)# interface vlan 99 - Configure VLAN interface
• Switch1(config-if)# ip address 192.18.9.1 255.255.255.0 - Assign IP address to VLAN
• Switch1(config-if)# no shutdown - Enable the interface
• Switch1(config-if)# exit - Exit interface configuration
• Switch1(config)# interface GigabitEthernet0/1 - Configure physical interface
• Switch1(config-if)# switchport mode access - Set port mode to access

Port security commands

• Switch1(config-if)# switchport port-security - Enable port security
• Switch1(config-if)# switchport port-security maximum 1 - Set maximum MAC addresses
• Switch1(config-if)# switchport port-security mac-address sticky - Enable sticky MAC addresses
• Switch1(config-if)# switchport port-security violation shutdown - Set violation mode to shutdown

Password commands

• Switch1(config)#enable password Passwordmodai - Enable password
• Switch1(config)#enable secret Passwordmodai - Enable secret password
• Switch1(config)#line console 0 - Configure console line
• Switch1(config-line)#password Passwordmodai
• Switch1(config-line)#login

Verifying configuration

• Switch1# show startup-config

Changing switch name

• Switch1#config terminal
• Switch1(config)#hostname Loweswitch