Читать книгу CCNP Enterprise Certification Study Guide: Implementing and Operating Cisco Enterprise Network Core Technologies - Ben Piper, David Higby Clinton - Страница 34

When you think of the term subnet, you probably think of an IP subnet address and mask, such as 192.168.1.0/24. The IP subnet address and mask collectively form a CIDR block, or just CIDR for short. But a subnetwork (subnet) is actually a collection of connected nodes that all use the same Data Link layer protocol. For example, a collection of nodes in the same VLAN is an example of a subnetwork. To avoid confusion, I'll refer to the combination of IP subnet address and mask as either a CIDR or an IP subnet.

The moral of the convoluted story behind Ethernet and bridges is that no matter how many tricks and kluges you invent, you can't extend a subnet beyond a few hundred nodes. Regardless of the protocols used, the number of nodes in a subnet is limited by the underlying physical media. To create large networks that include thousands or millions of nodes, we need to join multiple subnets together. This brings us to the Network layer.