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IP Address

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IP Address

An IP address (Internet Protocol address) is a unique numerical identifier assigned to each device connected to a computer network that uses the Internet Protocol for communication. IP addresses serve two main functions: host or network interface identification and location addressing.

IP Address Versions

IPv4 (Internet Protocol version 4)

IPv4 uses a 32-bit address scheme allowing for approximately 4.3 billion unique addresses. Written in dotted-decimal notation (e.g., 192.168.1.1), where four octets are separated by periods.

IPv4 Address Classes:

  • Class A: 1.0.0.0 to 126.255.255.255 (16 million hosts per network)
  • Class B: 128.0.0.0 to 191.255.255.255 (65,534 hosts per network)
  • Class C: 192.0.0.0 to 223.255.255.255 (254 hosts per network)
  • Class D: 224.0.0.0 to 239.255.255.255 (multicast addresses)
  • Class E: 240.0.0.0 to 255.255.255.255 (experimental use)

Private IPv4 Address Ranges:

  • 10.0.0.0 to 10.255.255.255 (Class A private network)
  • 172.16.0.0 to 172.31.255.255 (Class B private networks)
  • 192.168.0.0 to 192.168.255.255 (Class C private networks)

IPv6 (Internet Protocol version 6)

IPv6 uses a 128-bit address scheme providing approximately 340 undecillion unique addresses (3.4×10^38). Written in hexadecimal notation separated by colons (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334).

IPv6 Address Types:

  • Unicast: One-to-one communication
  • Multicast: One-to-many communication
  • Anycast: One-to-nearest communication

Special IPv6 Addresses:

  • ::1/128: Loopback address (equivalent to 127.0.0.1 in IPv4)
  • ::/128: Unspecified address
  • 2001:db8::/32: Documentation prefix
  • fe80::/10: Link-local addresses

Subnetting and CIDR

Subnet Masks

Subnet masks determine which portion of an IP address identifies the network and which identifies the host. Common subnet masks include:

  • 255.0.0.0 (/8) - Class A default
  • 255.255.0.0 (/16) - Class B default
  • 255.255.255.0 (/24) - Class C default

CIDR Notation

Classless Inter-Domain Routing (CIDR) expresses IP addresses and their routing prefix as a pair (e.g., 192.168.1.0/24), where the suffix indicates the number of bits in the network prefix.

Common CIDR Blocks:

  • /32: Single host (255.255.255.255)
  • /24: Small network (256 addresses, 254 usable)
  • /16: Large network (65,536 addresses, 65,534 usable)
  • /8: Very large network (16,777,216 addresses, 16,777,214 usable)

IP Address Allocation

Dynamic Allocation

  • DHCP: Dynamic Host Configuration Protocol automatically assigns IP addresses
  • Temporary leases: Addresses assigned for specific time periods
  • Address pools: Ranges of addresses available for dynamic assignment

Static Allocation

  • Manual configuration: Fixed addresses set by administrators
  • Reserved addresses: Important devices (servers, routers, printers)
  • DNS integration: Static mappings for consistent name resolution

Address Resolution

ARP (Address Resolution Protocol)

Maps IPv4 addresses to MAC addresses in local networks:

  1. Device broadcasts ARP request for IP address
  2. Device with matching IP responds with MAC address
  3. Mapping cached for future use

Neighbor Discovery Protocol (IPv6)

IPv6 equivalent of ARP with additional functionality:

  • Address autoconfiguration
  • Duplicate address detection
  • Router discovery

IP Address Management (IPAM)

Enterprise Considerations

  • Address planning: Structured allocation of IP ranges
  • Documentation: Maintaining accurate address records
  • Monitoring: Tracking address utilization and conflicts
  • Automation: Tools for managing large-scale deployments

Tools and Solutions

  • Spreadsheet tracking: Small networks
  • Dedicated IPAM software: Enterprise environments
  • Network management systems: Integrated solutions
  • Cloud-based services: Scalable management platforms

IPv4 to IPv6 Transition

Transition Technologies

  • Dual stack: Running both IPv4 and IPv6 simultaneously
  • Tunneling: Encapsulating IPv6 traffic in IPv4 networks
  • Translation: Converting between IPv4 and IPv6 addresses

Deployment Strategies

  • Gradual migration: Phased approach by network segments
  • Hybrid environments: Supporting both protocols during transition
  • Native IPv6: Direct IPv6 connectivity where available

Security Considerations

IP Address Spoofing

  • Source address validation: Verifying packet origins
  • Ingress/egress filtering: Preventing forged addresses
  • Authentication mechanisms: Securing address assignments

Network Segmentation

  • Subnet isolation: Separating network segments
  • Access control: Restricting communication between subnets
  • VLAN implementation: Logical network separation

Troubleshooting IP Address Issues

Common Problems

  • IP conflicts: Duplicate addresses on the same network
  • Configuration errors: Incorrect subnet masks or gateways
  • DHCP failures: Servers not responding or exhausted pools
  • Resolution failures: DNS or ARP issues

Diagnostic Tools

  • ipconfig/ifconfig: Display IP configuration
  • ping: Test connectivity to specific addresses
  • tracert/traceroute: Trace network paths
  • nslookup/dig: DNS resolution testing
  • arp: Display and manage ARP tables

References

  • IETF RFC 791: Internet Protocol (IPv4)
  • IETF RFC 2460: Internet Protocol, Version 6 (IPv6) Specification
  • IETF RFC 1918: Address Allocation for Private Internets
  • IETF RFC 4632: Classless Inter-domain Routing (CIDR)

Backlinks

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