Cisco Systems CCNA 2 manual Router LANs and WANs, Rom

•Memory

•Interfaces

However, the main purpose of a router is to route, not to compute. The main components of the router are as follows:

•RAM

•NVRAM

•Flash

•ROM

•Interfaces

The following topics should be covered in this TI:

•Discuss the similarities of computers and routers such as the software they use.

•Explain the components of the router and what each component contains.

•Open a router and let the students examine the inside. Point out the main components.

•Explain that just as a computer cannot work without an operating system and software, a router cannot work without an operating system and configurations.

1.1.3Router LANs and WANs

Routers function in both LANs and WANs. They are primarily used in WANs. Explain that routers have both LAN and WAN interfaces. Students should be able to identify the differences. The two main functions of a router are to select the best path and to forward packets to the correct outgoing interfaces.

Networking models are useful because they facilitate modularity, flexibility, and adaptability. Like the OSI model, the three-layer design model is an abstract picture of a network. Models may be difficult to comprehend because the exact composition of each layer varies from network to network.

Explain that each layer of a three-layer design model may include a router, a switch, a link, or some combination of these. Some networks may combine the function of two layers into a single device or may omit a layer entirely. The three-layer design model consists of the following:

•The core layer forwards packets as quickly as possible.

•The distribution layer provides a boundary by using filters to limit what gets to the core.

•The access layer feeds traffic into the network and controls entry into the network.

12 - 238 CCNA 2: Routers and Routing Basics v3.1 Instructor Guide – Module 1 Copyright ♥ 2004, Cisco Systems, Inc.