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 […]
Cisco Show Interface Command on Routers and Switches Explained
One of the most useful and popular commands used on Cisco devices is the “show interface” command. It can be very useful at troubleshooting connectivity issues and physical port issues, check the status of physical ports, watch how much traffic is passing through the interface, which IP address is assigned to the interface (for Layer3 […]
Layer 2 VLAN Configuration on a Cisco Switch (with Example)
This post will deal with creating Layer 2 VLANs on Cisco switches and performing all relevant configurations. Up to 4094 VLANs can be configured on Cisco catalyst switches. By default, only VLAN 1 is configured on the switch, so if you connect hosts on an out-of-the-box switch they all belong to the same Layer 2 […]
How to Configure L2 and L3 InterVlan Routing on Cisco Nexus Switches
Although we live in an era of network virtualization and software defined networking, the traditional hardware ethernet switch is still at the backbone of most networks. Cisco switches have been among the leaders in this field. The original Catalyst series of switches (running on IOS software) are still in production and powering millions of networked […]
Basic Cisco Switch Configuration
In my opinion, the Cisco switches are the best in the market. Versatile, reliable, flexible and powerful, the Cisco switch product line (such as the 2960, 3560, 3650, 3850, 4500, 6500, 9400 series etc) offer unparalleled performance and features. Although a Cisco switch is a much simpler network device compared with other devices (such as […]
Cisco Spanning Tree Protocol Guide (STP Examples and Configuration)
Spanning Tree Protocol (STP) ensures a loop-free topology in a local area network (LAN) made up of switches. It is desirable to have redundant links in a switched LAN so that a single link failure cannot interrupt normal operation of the network. But redundant links may also introduce physical switching loops that are undesirable. STP […]
Private VLAN Configuration on Cisco Switches (Example Configuration)
We know that a Layer 2 VLAN is an isolated Broadcast Domain and for communicating between VLANs a Layer 3 Device is required (either router or Layer3 switch) for inter-VLAN Routing. A Private VLAN gives us the opportunity to divide a VLAN into Sub VLANs. In the case of PVLAN, a normal Layer 2 VLAN […]