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 […]

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. […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

UPDATED: 2020 – Cisco Catalyst switches equipped with the Enhanced Multilayer Image (EMI) can work as Layer 3 devices with full routing capabilities. For example, some switch models that support layer 3 routing are the 3550, 3750, 3560 etc. On a Layer3-capable switch, the port interfaces work as Layer 2 access ports by default, but you […]

In this article we will describe how to configure both LACP and PAgP EtherChannels on Cisco switches. An EtherChannel is a Link Aggregation technology whereby two switches are connected together with multiple interfaces which are bundled together to form a single logical interface (“Port-Channel”) therefore increasing bandwidth between the switches. EtherChannel Use-Case The diagram below […]