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Computer networks

Free IP addressing and routing lessons

8 lessons, about 2 hours in all. Each teaches one idea with a visual, then gives you a problem or a few questions on it. Read the lessons here, then create a free account to practise and keep your progress.

Start free with lesson 1See the full IP addressing and routing path

Stage 0Addresses and subnets

  1. IPv4 addressesRead an address as network and host parts, and know the private and special ranges.12 min
  2. Subnet masks and CIDRUse a prefix length to find a subnet's network address, broadcast address and host range, and test whether two hosts share one.15 min
  3. Subnetting and aggregationSplit one block into subnets, size each for the hosts it needs, and combine neighbouring blocks into one route.14 min

Stage 1Forwarding and routing

  1. Forwarding and longest-prefix matchSee how a router chooses an outgoing interface from its table when several entries match.13 min
  2. Distance-vector routingLet routers learn routes by trading their distance tables with neighbours, and see how bad news travels slowly.15 min
  3. Link-state routing and DijkstraFlood every router's links to everyone, then let each router compute shortest paths itself.15 min

Stage 2NAT, ICMP and IPv6

  1. Network address translationSee how many private hosts share one public address by rewriting ports, and what that breaks.12 min
  2. ICMP and IPv6See how ping and traceroute use ICMP and the TTL, and what IPv6 changes about addresses and headers.13 min

All of IP addressing and routing is free

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