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Beginner Course · For complete beginners

A Journey in Ten Stops

Travel with Pip the Packet, starting from the MAC Address and moving stop by stop until the moment a website opens. Each lesson takes 5 to 10 minutes.

10 lessons · 10 ready to read

Start with Lesson 1 Open the course map

Network Stories

One story, one network feature

The Network Buddies run into the same troubles real networks face, then discover the clever fixes engineers came up with. We start with the humble Switch, and story by story the pieces join up into the bigger picture.

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Part 1: Inside One LAN (Layer 2)

  1. Beginner About 10 min 1. Octo's First Day: How a Switch Delivers Three computers want to share photos with each other. Can we just run a cable between every pair? SwitchMAC AddressFrame Recommended first: Lesson 3
  2. Beginner About 10 min 2. Octo's Predecessor: Hubs and Collisions What happens if everyone talks at the same time? HubCollisionSwitchEthernet Recommended first: Story 1: “Switch Basics”
  3. Beginner About 10 min 3. Who Is 192.168.1.11? ARP (Address Resolution Protocol) If you only know someone's IP Address, how do you find their MAC Address? ARPIP AddressMAC AddressBroadcast Recommended first: Lesson 4, Story 1: “Switch Basics”
  4. Beginner About 10 min 4. The Invisible Cable: Wi-Fi and Access Points Your phone has no network cable plugged in. So how does its data get into the LAN? Wi-FiAccess PointSSID Recommended first: Story 1: “Switch Basics”
  5. Intermediate About 10 min 5. One House, Two Zones: VLAN (Virtual LAN) Why can't the guest Wi-Fi see the computers in your home? VLANSwitchBroadcast Recommended first: Story 1: “Switch Basics”, Story 3: “ARP”
  6. Intermediate About 10 min 6. One Cable, Many Zones: Trunks and 802.1Q Tags There's only one cable between two Switches. How can it carry data for two VLANs at once? VLANTrunkSwitch Recommended first: Story 5: “VLAN”
  7. Intermediate About 10 min 7. Octo's Broadcast Storm: Spanning Tree Protocol Adding an extra cable should make the network more reliable. So why did the whole LAN grind to a halt? SwitchBroadcastSTP Recommended first: Story 1: “Switch Basics”
  8. Intermediate About 10 min 8. Two Cables Pulling Together: Link Aggregation STP switched off the spare cable. Is there a way to use both cables at once? Link AggregationSwitchLACPSTP Recommended first: Story 7: “Spanning Tree”

Part 2: Leaving the LAN (Layer 3)

  1. Beginner About 10 min 9. Out the Front Door: Router and Default Gateway Octo can't deliver to other networks. So who should the letter be handed to? RouterDefault GatewayLayer 3 Recommended first: Lesson 4, Story 3: “ARP”
  2. Intermediate About 10 min 10. A Bridge Between Zones: Inter-VLAN Routing The family zone and the guest zone are kept apart. But sometimes they need to talk. How? Inter-VLAN RoutingVLANRouterLayer 3 Switch Recommended first: Story 6: “Trunks and 802.1Q”, Story 9: “Router and Default Gateway”
  3. Intermediate About 10 min 11. The Art of Cutting Cake: Subnetting There's only one block of addresses, but it has to be shared by three networks. How do you cut it just right? SubnettingSubnetIP AddressCIDR Recommended first: Lesson 4, Story 9: “Router and Default Gateway”
  4. Intermediate About 10 min 12. Rue's Map: Routing Tables and Static Routes How does Rue know the "next stop" for every letter? RouterRouting TableStatic Route Recommended first: Story 11: “Subnetting”
  5. Intermediate About 10 min 13. The Routers Swap Notes: Dynamic Routing and OSPF A city has a hundred Routers. Who keeps every single map up to date? RouterOSPFDynamic Routing Recommended first: Story 12: “Routing Table”
  6. Intermediate About 10 min 14. The Building Office: NAT and Port Forwarding A whole family shares one Public IP. So how does each reply find the right person? NATPort ForwardingPortPrivate IP Recommended first: Lesson 8, Lesson 9

Part 3: Transport and Services

  1. Intermediate About 10 min 15. Did Pip Arrive Safely? TCP Sequence Numbers and ACKs A photo is cut into lots of packets. What happens if one goes missing? TCPSequence NumberACKRetransmission Recommended first: Lesson 9
  2. Beginner About 10 min 16. The Network Doctor: ICMP, Ping and Traceroute When you can't get online, how do you find out which stop the problem is at? ICMPPingTracerouteTTL Recommended first: Story 9: “Router and Default Gateway”, Story 12: “Routing Table”
  3. Intermediate About 10 min 17. The Sealed Letter: HTTPS and TLS What exactly does the padlock next to the web address lock up? HTTPSTLSDigital Certificate Recommended first: Lesson 10

Part 4: Security and Reliability

  1. Intermediate About 10 min 18. The Secret Tunnel: VPN (Virtual Private Network) When you're online in a coffee shop, how can you safely connect back to your home or office network? VPNEncryptionTunnel Recommended first: Story 17: “HTTPS and TLS”, Story 14: “NAT and Port Forwarding”
  2. Intermediate About 10 min 19. The Guard at the Door: Firewalls and ACLs Every packet wants to come in. How does Pango decide which ones to let through and which ones to stop? FirewallACLPort Recommended first: Story 14: “NAT and Port Forwarding”, Story 15: “TCP Reliable Delivery”
  3. Intermediate About 10 min 20. No Fear of Crowds: Load Balancers and High Availability When millions of people open the same website at the same time, why doesn't the server collapse? Load BalancerHigh AvailabilityDNS Recommended first: Story 19: “Firewall and ACL”, Lesson 7

Part 5: One-to-Many Delivery

  1. Beginner About 10 min 21. Unicast, Broadcast, Multicast & Anycast Two TVs want to watch the same live match. Should we send two copies, or one copy to the whole house? MulticastUnicastBroadcastAnycast Recommended first: Lesson 3, Lesson 4, Story 1: “Switch Basics”
  2. Intermediate About 10 min 22. IGMP Snooping The TV in the living room is showing a live stream. So why is the phone in the study so slow online? MulticastIGMPSwitch Recommended first: Story 21: “Multicast”, Story 4: “Wi-Fi and Access Points”

Network Buddies Pro

Engineer mode: set up real networks

Finished the stories and curious how real network equipment is set up? Pro is split into Layer 2 and Layer 3. Every lesson has a topology diagram, commands, a guide to reading show output, and a CLI Lab where you can type commands right in your browser.

Open the Pro index

Layer 2 Pro

  1. VLAN and TrunkPlanned
  2. STP Deep DiveIncludes CLI Lab
  3. EtherChannelPlanned
  4. Layer 2 SecurityPlanned
  5. CDP and LLDPPlanned

Layer 3 Pro

  1. Routing DecisionsPlanned
  2. Static RoutesPlanned
  3. OSPF Deep DivePlanned
  4. FHRPPlanned
  5. NAT/PAT and DHCP RelayPlanned
  6. ACL Deep DivePlanned
  7. IPv6 in PracticePlanned
  8. BGP BasicsPlanned