How to combine two graphs on Cacti

Cacti is a fantastic open source network monitoring system that is widely used to graph network elements like bandwidth, storage, processor and memory utilization. Using its web based interface, you can create and organize graphs easily. However, some advanced features like merging graphs, creating aggregate graphs using multiple sources, migration of Cacti to another server […]
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How to secure BGP sessions using authentication on Quagga

The BGP protocol runs over TCP, and as such, it inherits all the vulnerabilities of a TCP connection. For example, within a BGP session, an attacker may impersonate a legitimate BGP neighbor, and convince the BGP routers on the other end to share their routing information with the attacker. The problem occurs when the attacker […]
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How to perform BGP traffic engineering using Quagga on Linux

The previous tutorials demonstrated how we can turn a CentOS box into a BGP router and filter BGP prefixes using Quagga. Now that we understand basic BGP configuration, we will examine in this tutorial how to perform more advanced traffic engineering on Quagga. More specifically, we will show how we can influence the routing path […]
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How to set up IPv6 BGP peering and filtering in Quagga BGP router

In the previous tutorials, we demonstrated how we can set up a full-fledged BGP router and configure prefix filtering with Quagga. In this tutorial, we are going to show you how we can set up IPv6 BGP peering and advertise IPv6 prefixes through BGP. We will also demonstrate how we can filter IPv6 prefixes advertised […]
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How to filter BGP routes in Quagga BGP router

In the previous tutorial, we demonstrated how to turn a CentOS box into a BGP router using Quagga. We also covered basic BGP peering and prefix exchange setup. In this tutorial, we will focus on how we can control incoming and outgoing BGP prefixes by using prefix-list and route-map. As described in earlier tutorials, BGP […]
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How to turn your CentOS box into a BGP router using Quagga

In a previous tutorial, I described how we can easily turn a Linux box into a fully-fledged OPSF router using Quagga, an open source routing software suite. In this tutorial, I will focus on converting a Linux box into a BGP router, again using Quagga, and demonstrate how to set up BGP peering with other […]
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How to turn your CentOS box into an OSPF router using Quagga

Quagga is an open source routing software suite that can be used to turn your Linux box into a fully-fledged router that supports major routing protocols like RIP, OSPF, BGP or ISIS router. It has full provisions for IPv4 and IPv6, and supports route/prefix filtering. Quagga can be a life saver in case your production […]
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How to use logrotate to manage log files in Linux

Log files contain useful information about what is going on within the system. They are often inspected during troubleshooting processes or as part of server performance analysis. For a busy server, log files may grow quickly into very large sizes. This becomes a problem as the server will soon run out of space. Besides, opening […]
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How to monitor server memory usage with Nagios Remote Plugin Executor (NRPE)

In a previous tutorial, we have seen how we can set up Nagios Remote Plugin Executor (NRPE) in an existing Nagios setup. However, the scripts and plugins needed to monitor memory usage do not come with stock Nagios. In this tutorial, we will see how we can configure NRPE to monitor RAM usage of a […]
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