These notes introduce core IPv4 concepts:
They then outline basic routing behavior with longest-prefix matching and present the fundamentals of IPv4 multicast, including addressing, group membership via IGMP (Internet Group Management Protocol), LAN mapping, and inter-network distribution. The notes emphasizes exact notation (prefix lengths and netmasks), validity of network IDs, and a simple routing-table example. They close with a status note on multicast deployment, highlighting common constraints and typical use scopes.
An IP address is a 32-bit identifier assigned to host or router interfaces. The network part corresponds to the high-order bits of the address, while the host part corresponds to the low-order bits. An IP network is the set of IP devices whose interfaces share the same network part of the IP address and are connected to the same physical (link-layer) network.
The image illustrate these notions with addresses such as 223.1.1.1, 223.1.1.2, 223.1.1.3, 223.1.1.4, 223.1.2.9, 223.1.2.2, and 223.1.2.1.
Classful addressing is summarized with bit positions and first-byte ranges.
CIDR (Classless InterDomain Routing) permits a network portion of arbitrary length. Address format uses either network ID + prefix length notation (e.g., 200.23.16.0/23) or netmask notation (e.g., 200.23.16.0 255.255.254.0). The netmask consists of all ‘1’s in the network part and all ‘0’s in the host part.
The image illustrates the split with a 32-bit binary example labeled “network part” and “host part.”