Network Concepts

OSI Model to Describe Network Operations

Layer 7: Application Layer

Layer 6: Presentation Layer

Layer 5: Session Layer

Layer 4: Transport Layer

Layer 3: Network Layer

  1. Terms and Concepts

Layer 1: Physical Layer

  1. Port Mirroring * Takes all the traffic and mirrors the traffic from the switch to another computer so you can analyze the traffic
  2. Power over Ethernet PoE
  • IEEE 802.3
  • Fiber Optics
    1. Cabling
      • Single Mode
        • Very thin, laser passes though for long distances
        • Usually Yellow jacket/insulation
      • Multi Mode
        • Thicker glass, cheaper to make, use in applications which are shorter, laser light bounces around in fiber which reduces single strength.
        • Usually has Orange or Aqua jacket/insulation
    2. NIC Lasers and Fiber Optic
      Mode Laser Type Wavelength Fiber Distance
      Single Mode LX 1270-1610nm Single Mode 70 km
      Multi Mode SX 770-860 nm Multi Mode 1/2-1km
    3. Optical Network Interface Cards (Optics, lasers)
      • GBIC (old)
      • SFP (small form pluggable)
      • Plug into switch, server or other network device
      • QSFP and QSF+ (newer form of NIC cards, Q means Quad.)
      • Connectors( ST Connector, SC Connector, LC Connector, MTRJ Connector, FC Connector)
      • Patch Panel, terminate in one spot then use shorter piece of fiber to plug into the patch panel, to plug in to the SFP into the gear.
    4. Connections: Angled physical contact (APC) or Ultra Physical Contact (UPC)
    5. Operation: light and data flow one way in one fiber and the other way, called Simplex Pair, with lasers and eyes on both ends. But can be one fiber, called Bidirectional with different wavelengths of light via WDM (Wave division Multiplexing). WDM works by using three different kind of UV lasers shining into a prism and create a single stream of light, and then another prism breaking it out into each eye.
    6. Wave Division Multiplexing
      • coarse wave division multiplexing, CWDM, and is passive.
      • Dense Wave Division Multiplexing, Powered, longer distance, more wavelengths.
    7. Fiber Ethernet Designation and Cabling Type
      100BaseFX Multi Mode Fiber
      100BaseSF Multi Mode Fiber
      1000BaseSX Multi Mode Fiber
      1000BaseLX Single Mode Fiber
      10GBaseSR Aqua mostly but some orange Multi Mode Fiber
      10GBaseLR Single Mode Fiber
  • Protocols:

    Encapsulation and the OSI Model

    1. Application Layer breaks up data into Transport Layer
      • Segment: a chunk of data with a transport lawyer header, we put in a source and destination port number, and this port number is going to be directly related to an application layer protocol
    2. Transport layer becomes the payload for the Network Layer which is called a Packet
    3. Network Layer packet goes into the Data Link Layer payload into a Frame
      • Frame: a chunk of data with a Data Link layer header -- Ethernet MTU(Maximum Transmission Unit) is 1500 Bytes Including Packet Header and Segment header
    4. Link Layer sends the Frame down to the Physical Layer which breaks it into ones and zeros, and then that is converted into a signal

    Routing IP Traffic

    1. Require Physical, Data Link (traffic from one device to another) and Network layer (Internet Layer with routers to move traffic from one segment of the network to another, and if Layer 2 Bridge like a cable Modem that converts Ethernet frames and puts it in a DOCSIS frame (DOCSIS is protocol that cable modem uses to communicate to ISP)
    2. IP Packet
      • IP Packet contains:
        • Source IP Address
        • Destination IP Address
        • TTL (counter every time it goes through a router it deceases).
        • Other
        • ICMP (Ping uses ICMP protocol)
      • Layer 2 Frame
        • Destination MAC Address
        • Source MAC Address
        • Layer 3 Protocol

    Binary Counting

    128s 64s 32s 16s 8s 4s 2s 1s
    1 1 0 0 0 0 0 0

    Multiple placeholder by placeholder itself. Example: 11000000 is equal t 128 + 64 = 192

    Converting Decimal to Binary

    128s 64s 32s 16s 8s 4s 2s 1s

    Example: 210

    128s 64s 32s 16s 8s 4s 2s 1s
    YES Yes No Yes No No Yes No
    210-128= 82 82-64=18   18-16=2     2-2=0  
    1 1 0 1 0 0 1 0

    Example: 47

    128s 64s 32s 16s 8s 4s 2s 1s
    No No Yes No Yes Yes Yes Yes
        47-32=15   15-8=7 7-4=3 3-2=1 1-1=0
    0 0 1 0 1 1 1 1


    Binary Decimal Hexadecimal
    0000 0 0
    0001 1 1
    0010 2 2
    0011 3 3
    0100 4 4
    0101 5 5
    0110 6 6
    0111 7 7
    1000 8 8
    1001 9 9
    1010 10 A
    1011 11 B
    1100 12 C
    1101 13 D
    1110 14 E
    1111 15 F
    10000 16 10

    IP Addressing


    Street Address Zip Code
    123 Main Street 60787


    Classful vs Classless addressing

    Address Types

    1. Network Address:
      • Identifier for a group of devices
      • "Network Prefix"
      • Have all Zeros in the Host portion.
        Network Portion Network Portion Network Portion Host Portion
        . . . .
        203 0 113 10
        11001011 00000000 01110001 00001010
        11111111 11111111 11111111 00000000
        255 255 255 0
    1. Broadcast Address:
      • Identifier for all devices on a network.
      • It allows a sender to send a message to every single device on the network.
      • Have all 1's in host portion
        Network Portion Network Portion Network Portion Host Portion
        . . . .
        203 0 113 255
        11001011 00000000 01110001 11111111
        11111111 11111111 11111111 00000000
        255 255 255 0
    1. Host Address:
      • Identifies unique device on a network.
      • Identifies a unique device on the network, combo of network portion of address and host portion of address, where the host portion isn't identifying a network address nor the broadcast.
      • Anything EXCEPT all binary 0's or 1's
        Network Portion Network Portion Network Portion Host Portion
        . . . .
        203 0 113 10
        11001011 00000000 01110001 00001010
        11111111 11111111 11111111 00000000
        255 255 255 0


    IP Routing


    CIDER Classless Inter-Domain Routing

    Private IP Addresses

    Subletting Basics

    Network: Range: - Network: 00001010 | 00000000 00000000 00000000 Broadcast: 00001010 | 11111111 11111111 11111111

    11111111 00000000 00000000 00000000

    Lets find a host address on this network. Host: 00001010 00000000 00001010 00000000

    Change it to a /24 network: Network: 00001010 00000000 00010010 | 00000000 Broadcast: 00001010 | 00000000 00001010 | 11111111 So this network now has 254 different hosts. Zero to 255 is 256 unique address but but remove network address which you cant apply to a device and one for the broadcast address which you cant apply to a device. So now the network is -

    Variable Length Subnet Masking VLSM

    Its a way to break up /24 mask to be other kinds of masks:
    Cant just randomly pick IP addresses and masks and apply it to networks. Do have to make sure there is no overlap between subnets.


    IPV6 Address Components

    IPv4 Address Size

    IPv6 Addresses

    IPv6 Address Operation

    IPv6 Address Types

    IPv6 Address Acquisitions

    IPv6 DHCP

    IPv6 Tunneling

    Network Services

    Network Address Translation

    Dynamic Host Configuration Protocol

    Domain Name System

    Network Toplogies and Types

    Blank Area Networks

    Network Classifications

    WAN Technologies

    Virtualed Networks

    Network Monitoring

    Collecting Network Monitoring Data

    IT Documentation

    Network Drawings

    Corporate and Data Center Architectures

    Cloud Services

    Public, Private, Hybrid, Community Clouds

    Software as a service

    Platform as a service

    Infrastructure as a service

    Desktop as a service

    Cloud Benefits

    Network Troublehooting

    Irritive Troublehooting Methodology

    1. Identify the problem
      • Everyone has ego, and frusterations happen.
      • Talk and gather infomation. What can user can and cant do?
      • Identify the symptions.
      • Talk to other users and question users to figure out where issue is.
      • Change Managment, see if a change made by IT caused the issue.
      • Try and duplicate problem. If problem is not repeatable, dont disregard.
      • Multiple Problems, multiple things happening?
    2. Establish a theory of cause
      • Use OSI model to identify where the issue. Which will tell where to look further. Figure out what protocols and systems are involved in the system.
        • 7 Application Layer
        • 6 Presentation Layer
        • 5 Session Layer
        • 4 Transport Layer
        • 3 Network Layer
        • 2 Data Link Layer
        • 1 Physical Layer
      • Check your ego. Keep an open mind
    3. test the theory
      • Avoid Breaking network, keep ego in check, take care to not break stuff
      • Escalate to higher level
    4. estabish a plan of action
      • Examine required changes
      • change managment, to communcate changes to the systems, which dont need appovial, examin plan of action
      • Rollback plan, avoid a system wide action
    5. Implement a solution
    6. Verify solution
      • call to user to see if solution is good
      • IT is a service based org, kind friendly and helpfull for users to do their job
    7. Document solution

    Identifying and troubleshooting cable issues

    Cable Types and Distances      
    cable type material distance bandwidth
    ---- ---- ---- ----
    Cat 5/6/7 Copper 100M up to 10Gb
    Multi Mode SX Fiber 1km up to 100GB
    Single Mode LX Fiber 70 km up to 10Gb+

    CLI Utilities:

    Network Software Utilities

    Wireless troubleshooting and utilities

    Troubleshooting common PC networking issues

    Troubleshooting Layer 7 and above issues

    Smart Hands Training


    1. Patch panel labeling
    2. no standards in labeling
    3. Patch Panels
    4. 48 or 24 ports, identifier label or switch room identifier
    5. Patch cables is a patch panel to switch
    6. Use toner to find patch panel.
    7. Ports on a switch
    8. Odds on top, evens on bottom
    9. Switch stack number(1)/module number (0)/port number (GI is gigabit)
    10. 6-8-12 ports and 24-48 ports
    11. 9000 series switches
    12. Stacked switches are 1 to higher number from top to bottom
    13. Smaller switches
    14. Cascading Switches, connecting switches switches
      • MAC address tables of top switch will show Port example: 1 and mac address of each computer ex: DF 7B. and the Bottom switch will show Port example 1 and mac of the other computers on top switch, example: c2 a7 6e b3 3f
      • Broadcast messages can be a problem, with broadcast storm with messages if all the switches are connected to each other. Spanning Tree Protocol stops these broadcast storms but not all switches have STP
      • show mac address-table dynamic or CAM table table, Content Addressable directory and show one port show mac address-table interface int f0/1
      • KNow the IP address, find switchport:
        • no mapping on switch of IP address to switchport, as switch is layer 2 device, but all IP addresses are affilated with MAC addresses.
        • find out where is plugged into the switch, go from that local network segment (have to be on the workstation that can
        • look at AARP table on workstation, arp -a, show the mapping on the workstation of IP addresses to respective MAC addresses.
        • SSH into the Switch that the workstation is connected to. show mac address-table ? and the ? allows you to type the address mac address-table address 000c.292d.9200 which will show into the port. Then look at the network map and see what switch is connected to that port and SSH into that new switch, and show the mac address of the new swich show mac address-table address 000c.29ed.9200
        • show cdp neighbor will show all neighbors that are connected to the switch. nd remember that MAC address eventually get forgotten in MAC address Tables

    Switch Configuration

    Accessing a switch