Intro to Computer Science / Unit 9: The Internet and Networks
9.2 IP Addresses and DNS
Notes
Every device on the internet needs an IP address so data can be sent to the right place.
- IPv4 addresses have four numbers from 0 to 255, such as
192.168.1.10(32 bits). IPv6 addresses are much longer (128 bits) and were made because IPv4 addresses are running out. - People use names like
example.com. The Domain Name System (DNS) works like a phone book: it translates a domain name into an IP address. - Example: you type
example.com, your device asks a DNS server, gets the IP address, and then connects to it. - A domain is read right to left: in
www.example.com,.comis the top-level domain.
Practice
What does DNS do?
DNS looks up the IP address that belongs to a name.
Which of these looks like a valid IPv4 address?
An IPv4 address has four numbers from 0 to 255. 300 and 256 are too large.
Why was IPv6 introduced?
IPv6 has 128-bit addresses, giving far more addresses than IPv4.
Ready for more? Take the Unit 9 test.