Computer Networking › Section D · The network layer: data plane › Topic D.3
IPv4 datagrams and addressing
Every packet crossing the internet carries a small IPv4 or IPv6 header, and every router reads it. Knowing what is in the IPv4 header, and how its 32-bit addresses are carved into subnets and prefixes, is the key to reading forwarding tables and planning networks.
In this topic
- The IPv4 header
- Checksum and TTL
- Addresses belong to interfaces
- Subnets and CIDR notation
- Worked example: a /27 subnet
- Special addresses
- Route aggregation
- When a customer changes ISP
- Fragmentation
- Worked example: fragmenting a datagram
- Common mistakes to avoid
- Key takeaways
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