UPDATED: 2018 – 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 […]
Cisco Router-on-a-stick with Switch
Updated: 2018 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 […]
Cisco Switch EtherChannel Configuration – LACP – PAgP
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 […]
Cisco Switch Commands Cheat Sheet (CLI)
Cisco switches can be used as plug-and-play devices out of the box but they also offer an enormous amount of features. Although the main purpose of the switch is to provide inter-connectivity in Layer 2 for the connected devices of the network, there are myriad features and functionalities that can be configured on Cisco Switches. […]
Cisco Switch Port Security Configuration
Introduction One of the best practices in network security is to try and stop security threats from the entry-point of a LAN network. This means that the switch can play an important role in network security since it’s the entry-point of the network. For example, port- security on Cisco switches can be used to stop […]
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 Private VLANs on Cisco Switches
There are some situations where you have a single Layer3 subnet hosting several servers but you need to restrict network connectivity between the servers, although they reside in the same L3 subnet. This scenario is very common in hosting environments where you offer collocation for customers but for security reasons you want to keep their traffic […]
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 […]
Cisco Spanning Tree Protocol Discussion
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 […]
VLAN access-map (VACL) Example Configuration on Cisco Switch
In this post I will discuss Vlan access control lists (VACL), also called VLAN access Map or VLAN Map. A VLAN Access-map allows us to filter incoming and outgoing traffic in a switch Vlan. VLAN access-map configuration is very similar to the Route-map configuration. A Vlan access-map is placed on the whole Vlan, which means […]
Private Vlan Configuration
We know that a Layer 2 VLAN is an isolated Broadcast Domain and for communicating between VLANs a Layer 3 Device is required 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 VLAN is mapped on Secondary VLANs. This helps […]
Cisco Switching Products
Cisco Systems Inc. supports a broad range of local area network (LAN) switching architecture technologies and platforms. The general minimal requirements that the Cisco switching platforms are designed to address include the following: High-performance switched Ethernet, capable of delivering 100 Mbps and 1Gbps to the desktop, and 1Gbps or 10Gbps uplinks. Quality of Service (QoS) […]
Deleting the VLAN Database from a Cisco Switch
If you have your own Cisco switch equipment at your home lab or at your work environment you might have encountered the situation that you want to completely erase the whole switch configuration including any VLANs that are already configured on the switch (usually the vlan.dat file). In a Cisco switch, erasing the switch startup […]
