A switch is a network device that interconnects host devices at Layer 2 of the OSI model. In order to perform its function correctly, it must be able to learn the MAC addresses of the connected hosts and maintain them in a MAC address table. In this article, I’ll explain in detail how a switch […]
How to Find a Device MAC Address on a Cisco Switch (show mac address-table)
When performing troubleshooting or maintenance tasks on an enterprise network, it is sometimes necessary to identify the MAC address of particular devices (hosts, other switches, other network devices) that are connected to the network. On smaller networks, this is somewhat simple to achieve, however, on larger networks, it can become a challenge. In this article, […]
How to Configure a Loopback Interface on Cisco Router & Switch
A loopback interface is a virtual interface that can be created within a network device and behaves much the same as a physical interface. Loopback interfaces can be configured on a Cisco router or a switch and have many uses. In this article, we’ll examine what they are, how they can be configured, and how […]
Cisco Switch Layer2 Layer3 Design and Configuration
Layer2 and Layer3 switches are the foundation of any network. After all, any network devices (routers, firewalls, computers, servers etc) have to be connected to a switch. Sooner or later, as a network engineer you will be faced with the task of deploying a switch network for a customer or for your own company. Therefore, learning […]
Description of Switchport Mode Access vs Trunk Modes on Cisco Switches
In this article, we will discuss a couple of core concepts of network switching which are about Access and Trunk ports and how to configure them using “switchport mode access” and “switchport mode trunk” commands on Cisco switches We will also delve into what a VLAN is, why they’re used and how all of this […]
What is an SFP Port-Module in Network Switches and Devices
A Small Form Factor Pluggable (SFP) Port on a network switch is an Ethernet Interface which has been designed to allow a small module (which contains a connector and small circuit board) to be inserted into the switch. This device is called an SFP Module. There are different types of SFP modules and SFP ports, […]
8 Different Types of VLANs in TCP/IP Networks
A VLAN (Virtual Local Area Network) is a fundamental concept in TCP/IP computer networks and every professional in this field must have a deep understanding of this technology. In networking, VLANs are implemented and configured on Ethernet Switches and they work at OSI Layer 2. They are a method to logically separate Layer 2 Ethernet […]
The Most Important Cisco Show Commands You Must Know (Cheat Sheet)
If you are a networking professional that is operating and supporting Cisco devices and networks, then learning some important “show commands” is essential. There are a few different categories of commands on Cisco devices. There are commands that configure the device to perform a certain function and also there are commands that extract information from […]
Traffic Filtering on Cisco Layer3 Switches using ACL and VACL
Cisco devices offer excellent features for traffic filtering. The classic Access Control List (ACL) is the core mechanism on Cisco network devices (routers, switches etc) which is mainly used for traffic filtering. In this article we will examine a different type of ACL, called the Vlan Access Control List (VACL) which works a little different […]
How to Configure Cisco Router-on-a-stick with Switch
In this post I will explain how to provide routing between two VLANs on a simple Layer 2 switch using a Cisco router with just one interface. This is called also Router-on-a-stick. This configuration is usually asked as a question in CCNA exams, so I hope it will be helpful for people preparing for certification. […]
Cisco DHCP Snooping Configuration – What is DHCP Snooping?
Nowadays enterprises should deploy any available defenses they have available in order to eliminate, or at least minimize, possible attacks in their networks. Security controls should start from the network itself and span the whole IT infrastructure up to the application level. In this article I will describe a simple and effective security protection which […]
What is VLAN Trunking and VTP – Configuration Example and Description
There are some networking terms and concepts that are so fundamental and important that every TCP/IP networking professional must know them by heart. One of these fundamental concepts is VLAN Trunking. What is VLAN Trunking in Networking? A VLAN Trunk falls into Layer 2 of the OSI model and is related to network switching. When […]
10 Different Types of Network Ethernet Switches for Small or Large Networks
Network Switches form the backbone of computer networks and are one of the main building blogs of a Local Area Network (LAN). A network switch usually operates at Layer 2 of the OSI model (working with the Ethernet protocol) but there are switch models that implement also routing, which can be considered as Layer 3 […]