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In this third installment of our Linux Foundation Certified Engineer Training Course sneak peek blog, we review LANs, WANs, VLANs and Bridges.

In parts 1 and 2  we reviewed the OSI network layers. Now we’re moving on to basic network topologies: local area networks (LANs), wide area networks (WANs), virtual local area networks (VLANs), and bridged networks. These are still the fundamental network designs, even in this fast-moving era of cloud, virtualization, and containers.

LAN: Local Area Network

Smaller network segments are sometimes referred to as collision domains, since there can be only one transmitter on the physical medium at a time. This is common in hub-based networks. Modern switch technology removes the restriction of one at a time, but the concept of broadcast domains still exists. Local Area Networks (LANs) are smaller, locally-connected networks, connected at Layer 2 by the same series of switches or hubs. The node-to-node communication happens at Layer 3, using the same network. Layer 2 to Layer 3 associations may use Layer 2 broadcasts and the ARP and RARP protocols to associate MAC addresses with IP addresses.

Bridged Network

A network bridge or repeater accepts packets on one side of the bridge and passes them through to the other side of the bridge. The effect is bi-directional:

• It is a combination of two or more networks at Layer 2.

• Bridged networks communicate as a single network.

WAN: Wide Area Network

A Wide Area Network (WAN) is a large and geographically diverse network. It is connected at Layer 3 from node to node.

VLAN: Virtual Local Area Network

A Virtual Local Area Network (VLAN) is a method for combining two or more separated LANs to appear as the same LAN. It is also a method for securing two or more LANs from each other on the same set of switches.

In part 4, “LFCE Prep Course: DNS Overview,” we’ll learn about the Domain Name System (DNS) protocol, include authoritative and recursive DNS servers, the DNS database, root DNS servers, and DNS command-line tools.

The Linux Foundation offers both certification tests and training, which you can read all about at Linux Foundation Training. You can become a Linux Foundation Certified Sysadmin, or a Linux Foundation Certified Engineer. In this series, you’ll get a look at our new Linux Foundation Certified Engineer prep course. The full LFCE course has 12 chapters. Over the next few weeks, we will preview “Session 2: Linux Networking Concepts and Review”.

Download the full sample chapter: Linux Networking Concepts and Review.