NET150 Class - eitan-j/tech-journal GitHub Wiki

11/3/2020

Static Routing

  • Routers move packets between networks
  • Routers choose where to route based on IP
  • Routing tables are needed to send to network that is not directly connected
  • Routing table needs
    • Network address
    • Subnet mask
    • Next hop
    • Physical interface
  • Static routing - hardcoded
    • Not well scalable
  • ip route {network destination ip} {destination subnet mask} {next hop IP}

10/27/2020

TCP/IP

  • Four layers
  • Network interface layer
    • Physical
    • Hub, switch
    • OSI 1-2
  • Internet layer
    • Addressing and routing
    • IP, ARP, ICMP, etc.
    • Router
    • OSI 3
  • Transport layer
    • Manages connections
    • TCP
      • Creates connection
      • Resends lost data
      • Three way handshake
    • UDP
      • Sends data
    • OSI 4
  • Application layer
    • OSI 5-7

DNS

  • Domain Name Server
    • Translates between human-friendly name and IP addresses

10/20/2020

  • Routing is needed for packets to cross multiple routers
  • tracert traces route

10/13/2020

More Subnetting

  • Lowest usable address - 1 above net address
  • Highest usable address - 1 below broadcast address
  • Use VLSM table
  • Subnets do not have to use the same mask
  • Largest subnets should go first

10/6/2020

Addressing and Subnetting

  • IP - 32 bits
  • Binary place value n is 2n
  • Net ID is at start - Host ID is rest
  • Subnet mask ANDs address to get net ID
  • If net IDs are same, in same network
  • Slash (CIDR) notation shows number of net ID bits
  • All 0s - lowest address - network address
  • All 1s - highest address - broadcast address
  • Number of subnets created is 2x where x is borrowed bits
  • Number of hosts is 2y where y is host bits (-2 for usable)
  • Some address ranges are private or reserved

10/2/2020

  • Straight-through cable - connects dissimilar devices
  • Cross-over cable - connects similar devices

9/22/2020

LAN

  • Switch
    • star topology
    • lookup table
    • layer 2
  • Hub
    • dumb
    • layer 1
  • Address Resolution Protocol - ask who is
  • ARP Cache - stores ARP info (lookup table)

9/14/2020

OSI Model - 7 layer network protocol

  • Layer 1 - physical layer - physical or EM ect. data
  • Layer 2 - data link layer - local using MAC and LLC
  • Layer 3 - network Layer - route based on IP address
  • Layer 4 - transport Layer - delivery and error correction
  • Layer 5 - session Layer - interacts with OS
  • Layer 6 - presentation Layer - translates data
  • Layer 7 - application Layer - user input and output

9/11/2020

Topologies

  • Star - central hub
  • Mesh - all connected to all others
  • Bus - connected in line
  • Ring - connected in ring

MAC address - address of specific device

  • OUI - maker number
  • Other part - assigned by maker

IP address - tells location in network

  • Network ID - first part of IP - Varies in length
  • Host ID - last part of IP - Specific device - Varies in length
  • IPv4 - ~4.3 billion addresses
  • IPv6 - ~79 octillion times more addresses
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