IP Addressing and DNS
1. IP Addressing: IPv4 vs. IPv6
An IP (Internet Protocol) address is a unique identifier assigned to every device on a network. Due to the explosion of "Internet of Things" (IoT) devices, the old IPv4 system ran out of addresses.
IPv4
- Size: 32-bit address.
- Format: 4 denary numbers separated by dots.
- Example:
192.168.1.1 - Capacity: ~4.3 billion addresses.
IPv6
- Size: 128-bit address.
- Format: 8 groups of hexadecimal characters.
- Example:
2001:0db8:85a3... - Capacity: 340 undecillion (virtually infinite).
2. Public vs. Private IP Addresses
- Public IP: Assigned by your ISP. This is the address the entire world sees when you are online.
- Private IP: Assigned by your router to devices inside your home/school. These are not visible from the internet.
Note: NAT (Network Address Translation) is the process your router uses to translate private IPs to your single public IP to save address space.
3. The Domain Name System (DNS)
The DNS is a hierarchical, distributed database that maps human-readable domain names (e.g., e-consult.co.ke) to machine-readable IP addresses.
1. Local Cache: Browser checks if it already knows the IP from a previous visit.
2. Recursive Resolver: If not, it asks the ISP's DNS server.
3. Root Nameserver: Directs the query to the correct TLD (Top Level Domain) server (e.g., .ke).
4. Authoritative Nameserver: Holds the actual IP records for the specific domain and sends it back.
5. Routing: The browser now knows the IP and establishes a connection.
4. Static vs. Dynamic IP
| Feature | Static IP | Dynamic IP |
|---|---|---|
| Description | Never changes. Manually assigned. | Changes periodically. Assigned via DHCP. |
| Common Use | Web Servers, VPNs, Printers. | Home smartphones, laptops. |
⚠️ AS-Level Exam Tip: If asked why IPv6 is better, don't just say "more addresses." Mention that it includes built-in security (IPSec), faster routing (no checksums), and simplifies network management (no NAT required).