Browsing articles in "Tutorial"
Nexus HSRP/VRRP active/active with vPC

In the article vPC aka Virtual PortChannel, I explained how vPC works and the benefits that it gives. However, there is another important feature using HSRP/VRRP protocols in the context of vPC: the Layer2 dual–active peer devices. What does it mean? HSRP and VRRP operate in active-active mode from data plane standpoint, as opposed to classical active/standby implementation with STP based network. From a control plane standpoint, active-standby mode still applies for HSRP/VRRP in context of vPC. A characteristic of the active HSRP/VRRP peer device is that it is the only one to respond to ARP requests for HSRP/VRRP VIP […]

vPC aka Virtual PortChannel

The vPC aka virtual Port Channel is a Cisco technology that presents both Nexus paired devices as a unique Layer 2 logical node to a third device. The third device can be a switch, server, or any other networking device that supports link aggregation technology. From a spanning tree standpoint, vPC eliminates STP blocked ports and uses all available uplink bandwidth. Spanning-Tree is used as a fail safe mechanism and does not dictate L2 path for vPC attached devices.  

Using Cisco ISE API to write web interface

In the last three months, I was involved in a project concerning the migration of the authentication system (dot1x) from Cisco ACS to Cisco ISE (1.4). At the end of this work, the account told me if it is possible to have a web interface with the active sessions, the devices authenticated via Dot1x and the devices authenticated via MAB. Reading the official guide, I found that Cisco ISE has embedded API. Cool! This what I needed!

SecureCRT: How to import sessions via CSV file

In my opinion, one of the best Telnet/Serial/SSH client is SecureCRT, that provides rock-solid terminal emulation for computing professionals, raising productivity with advanced session management and a host of ways to save time and streamline repetitive tasks. I recently had the need to import a hundred devices in SecureCRT, but I didn’t know how to do it. Surfing the web, I found a helpful python script to import it via CSV! Three components are required: SecureCRT (obviously), the script and the CSV file.

Is static port channel a good idea?

During my CCIE R&S studies (CCIE Routing and Switching v5.0 Official Cert Guide, Volume 1), I have discovered an unexpected behavior of the static port channel: a Layer2 loop! Obviously, in order for that happen, several things must happen. Suppose to have three switches:   The Ciscozine-ROOT switch, as the word suggest, is the root bridge (priority 4096); the Ciscozine-ROOT_SEC is the “backup root bridge” (priority 8192), while the Ciscozine-SW has the default priority.

Send WhatsApp alert during a network fault

A good network engineer must react quickly during a fault. On the market, there are several solutions to monitor the network malfunctions: HP Openview, Solarwinds, PRTG and other solutions (open source or not). Generally, when an alert/warning is detected an event is triggered: email, SMS or text to a monitor. But why don’t you send these messages via whatsapp? It’s free and can reach everyone, everywhere! What you need: PHP with openssl extension enabled WART WhatsAPI-Official SIM In this tutorial, I use XAMPP Portable version 1.8.3 ( on a Windows7 64bit machine. Note: The WhatsAPI-Official requires openssl extension enabled in the PHP settings; whitout this library the script cannot work! […]

Cisco VSS: Failure scenarios

In the last article, I explained how to configure the Cisco 6500 in VSS configuration, but how does the VSS reacts during a failure? There are three possible scenarios: Link failure within a multichassis Cisco etherchannel link Active supervisor engine failure VSL failure Scenario #1: Link failure within a multichassis Cisco etherchannel link Availability is not affected for those data flows that do not use the failed link. For those traffic flows that use the failed link, the effect consists of the time it takes to detect the link failure and reprogram the indices within the system.

Cisco 6500 VSS configuration

The Cisco Catalyst 6500 Series Virtual Switching System (VSS) allows the clustering of two chassis together into a single, logical entity. This technology allows for enhancements in all areas of network design, including high availability, scalability, management, and maintenance. The Virtual Switching System is created by converting two standalone Catalyst 6500 systems to a Virtual Switching System. The conversion is a one-time process that requires a few simple configuration steps and a system reload. Once the individual chassis reload, they are converted into the Virtual Switching System. All control plane functions are centrally managed by the active supervisor engine of the active virtual […]

How to log everything with SecureCRT

Unlike my technical articles about configurations, protocols and so on, in this tutorial I will explain how to log automatically all SecureCRT sessions. For those that are unaware, SecureCRT is one of the best SSH/telnet client. The question is “why save everything?” In my opinion, a good approach to work with many devices (network, security, …) is to save everything (show command, configuration command and so on..). This method gives several benefits, for instance when: The telnet/SSH client buffer is full Something goes wrong You mistakenly close SecureCRT You want to check what you have done

Send Cisco commands via SNMP

In the article “How to save configurations using SNMP“, I have explained how to get the Cisco configuration using SNMP. Now, I explain how to send commands via SNMP using the “ciscoConfigCopyMIB” MIB;  with this MIB, you can replace running/startup configuration, send commands, save the “show” output or reload the device. OK, let’s start :) First of all, check if your PC/Server has the SNMP suite; if not, install the net-snmp software (