Networking foundations
IP addresses, subnets, DNS, TCP and the ports behind every website, with diagnostics you can type.
By the end you can
- Read an IP address and its subnet mask
- Explain what DNS does before a page loads
- Tell TCP and UDP apart and know when each is used
- Diagnose a connection with ping, traceroute and dig
step 1 of 3
Addresses and subnets
Every device on a network has an IP address. IPv4 is four numbers, each 0 to 255.
The subnet mask says which part of the address is the network and which part is the device. /24 means the first 24 bits are the network, leaving 8 bits, so 254 usable addresses.
Private ranges (10.x, 172.16-31.x, 192.168.x) are reused inside homes and offices everywhere and are not routable on the public internet.
question 1 of 4
A machine has the address 192.168.1.40 with mask 255.255.255.0. Which part identifies the network?
question 2 of 4
How many usable addresses does a /24 network have?
question 3 of 4
Which of these can a device on the public internet route to directly?
question 4 of 4
Your laptop shows IP 169.254.11.3. What usually happened?