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7.8 IP address

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By So Hee Park 3 min read

CC by Aru

✅ IP Addresses (IPv4)

  • The IPs discussed here are IPv4.
  • IPv6 exists but is less widespread.
  • IPv6 addresses are longer.

✅ What is an IP Address?

  • An IP address identifies connections/devices in a network.

☑️ Structure of IPv4

  • 4 pieces of 8 bits.
  • 4 octets.
  • Total = 32 bits.
  • Followed by /number (prefix index).

☑️ Binary to Decimal Conversion

  • Uses powers/weights of 2.

✔️ Example

  • 11000000.10101000.00001010.00000100 /24

☑️ Conversion

  • 128 + 64
  • 128 + 32 + 8
  • 8 + 2
  • 4

☑️ Decimal Result

  • 192.168.10.4 /24

✅ IPs in Communication

  • IP bits travel in:

    • packets
    • headers

  • Every communication on the internet includes IP information.

✅ Devices with IP Addresses

  • Computers
  • Routers
  • Switches
  • Modems
  • Any network-connected device

☑️ Switch

  • Creates/manages connections.
  • Usually represented as a cube with arrows.

☑️ Router

  • Finds best path for packets.
  • Uses routing table.

✅ Identifying Networks and Hosts

  • IP identifies:

    • physical location
    • logical location

☑️ Prefix Index / Subnet Mask

  • Number after /.
  • Indicates how many bits identify the network.

☑️ Remaining Bits

  • Identify the host/device inside the network.

✅ Example of Net and Host

✔️ Binary IP

  • 00001010.11001010.00111010.01011010 /16

☑️ Decimal Conversion

  • 10.217.58.90 /16

☑️ Net Portion

  • 10.217.0.0

☑️ Host Portion

  • 0.0.58.90

✅ Subnet Mask

  • Alternative representation of prefix index.

☑️ Process

  • Write:

    • as many 1s as prefix bits
    • remaining bits as 0s

  • Convert to decimal.

✔️ Example

  • 11111111.11111111.00000000.00000000

☑️ Decimal Form

  • 255.255.0.0

✅ IP Address Management Organizations

  • 5 major organizations manage/sell IP addresses worldwide.

☑️ Examples

  • ARIN → North America
  • RIPE → Europe

☑️ ISP

  • ISP = Internet Service Provider.
  • ISPs buy IP ranges from these organizations.

✅ IPv4 Classes

  • There are 5 IP classes.

✅ Class A

☑️ Characteristics

  • /8
  • 8 bits = network
  • Remaining bits = hosts

☑️ First Octet Range

  • 1 → 126

☑️ Notes

  • Very few networks possible.
  • Huge number of hosts.
  • Used by massive companies.
  • Very expensive.

☑️ Subnet Mask

  • 255.0.0.0

☑️ Example

  • 100.x.x.x

✅ Class B

☑️ Characteristics

  • /16
  • 16 bits network
  • 16 bits hosts

☑️ First Octet Range

  • 128 → 191

☑️ Subnet Mask

  • 255.255.0.0

☑️ Example

  • 150.x.x.x

✅ Class C

☑️ Characteristics

  • /24
  • 24 bits network
  • 8 bits hosts

☑️ First Octet Range

  • 192 → 223

☑️ Notes

  • Very common in companies.

☑️ Subnet Mask

  • 255.255.255.0

☑️ Example

  • 200.x.x.x

✅ Class D

☑️ Purpose

  • Multicast communication.

☑️ First Octet Range

  • 224 → 239

☑️ Example

  • 225.x.x.x

✅ Class E

☑️ Purpose

  • Educational/training use.

☑️ First Octet Range

  • 240 → 254

☑️ Example

  • 250.x.x.x

✅ Local Host (LH)

☑️ Characteristics

  • Starts with 127.

☑️ Purpose

  • Testing connections.
  • Testing services locally.

✅ Communication Types

☑️ Unicast

  • One-to-one communication.

☑️ Broadcast

  • One-to-all communication.

☑️ Multicast

  • One-to-some communication.

✅ Special IP Classes

✅ Local Host

  • Starts with 127.

✅ APIPA

☑️ Characteristics

  • Starts with 169.

☑️ Meaning

  • No valid IP assigned.
  • Connection unreachable.

☑️ Causes

  • No signal.
  • DHCP failed.
  • Weak connection.

☑️ Notes

  • Used automatically in emergencies/weak channels.

✅ Private IPs

☑️ Private Ranges

  • 10.x.x.x
  • 172.x.x.x
  • 192.x.x.x

☑️ Characteristics

  • Only visible inside LAN (Local Area Network).

☑️ External Communication

  • Others usually see:

    • proxy IP
    • router IP

✅ Default Gateway

  • Usually the router IP.
  • First hop of communication.

☑️ Used When

  • No proxy exists.
  • Device has private IP.

✅ The Triplet

☑️ Components

  • IP address
  • Subnet mask
  • Default gateway

☑️ Purpose

  • Fully identifies:

    • network
    • host
    • fallback communication path

✅ Static vs Dynamic IPs

☑️ Static IP

  • Never changes.
  • Triplet visible in commands.

☑️ Dynamic IP

  • Assigned by DHCP.
  • Triplet not usually visible.
DAW bilingual, Computer System
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