Networking

Topics

1. 01

   What a network is

   Hosts, links, packets, switches and routers. Building a small network of your own to practise on.

   8 min
2. 02

   IP addresses

   IPv4 and IPv6 addresses, private and public ranges, network interfaces and the loopback, and an interface's MTU.

   12 min
3. 03

   Subnets and CIDR

   Network masks, CIDR notation, and working out which addresses are on the same network.

   10 min
4. 04

   The layers model

   The layers a packet passes through, what each one adds, and which tools work at which layer.

   11 min
5. 05

   Ports and sockets

   How one machine runs many services, well-known ports, seeing what is listening, and testing a port with nc.

   13 min
6. 06

   TCP

   Connections, the three-way handshake, connection states, and what reliable delivery costs.

   12 min
7. 07

   UDP

   Sending without a connection, where that is the right choice, and what can go missing.

   9 min
8. 08

   DNS basics

   How a name becomes an address, /etc/hosts and resolvers, record types, caching and TTLs, and following a lookup with dig.

   12 min
9. 09

   HTTP

   Requests and responses, methods, status codes, headers, redirects and JSON, and watching a request with curl.

   12 min
10. 10

    Serve a website with nginx

    Installing nginx, serving a site, server blocks, and reading its logs.

    9 min
11. 11

    TLS and HTTPS

    What TLS protects, certificates and the chain of trust, inspecting a site's certificate, and signing one with your own CA.

    13 min
12. 12

    Routing and gateways

    The routing table, the default gateway, and following a packet's path with traceroute.

    10 min
13. 13

    NAT

    How private addresses reach the internet, and forwarding a port from outside to a machine inside.

    11 min
14. 14

    Firewall basics

    Packet filtering, rules and chains, default policies, and locking down a server without locking yourself out.

    13 min
15. 15

    tcpdump

    Capturing packets, filtering them, and reading what was actually sent.

    10 min
16. 16

    SSH and tunnels

    Keys, the SSH config file, jump hosts, and forwarding ports through SSH.

    11 min
17. 17

    Reverse proxy and load balancing

    Putting nginx in front of applications and spreading requests across several of them.

    10 min
18. 18

    The debugging playbook

    A layer-by-layer method for working out why a service cannot be reached.

    10 min