Networking, Python, BigData and Linux

Introduction: The BGP flow specification (flowspec) feature allows you to rapidly deploy and propagate filtering and policing functionality among a large number of BGP peer routers to mitigate the effects of a distributed denial-of-service (DDoS) attack over your network. Flowspec model: The BGP Flowspec model comprises of a Client and a Server.The Controller is responsible for sending or injecting the flowspec NRLI entry. The client (acting as a BGP speaker) receives that NRLI and programs the hardware forwarding to act on the instruction from the Controller. In our setup, ExaBGP daemon acts as the flowspec server(Controller) and flowspec supporting cisco IOS-XR  routers act as flowspec clients. GNS topology consisting of IOS-XR routers as provider edge routers is created, and the provider edge routers are connected to the external network so that provider edge routers can talk to ExaBGP node as shown in diagram below. Hence, ExaBGP is respo...

There could be many cases where "error mounting filesystem failed" problem can occur. While starting up ubuntu returned this message with information "please run fcsk manually".After running following command in the debugging terminal solved the problem for me: fsck.ext2 /dev/sda1 (ext2 or sda1 depend upon ubuntu installation on your system). When i looked into the root cause of above error, it was due to improper shutdown.When the battery of the system reach to critically low level(almost 0%), then system goes off.This was the reason shutdown was improper.There could be many solution for this, i have one automated solution for this. In linux, "acpi" command returns the status of battery like % level of battery, charging/discharging etc.Now, we run a script that continuously monitors the status of battery and we can interrupt a graceful shutdown if battery label is below some threshold value and battery is discharging.How to do that?Just copy paste ...

Unix has strong commands/utilities to monitor/debug/control the network.Here are the 5 most useful tools: 1.Tcpdump: Tcpdump, very popular network debugging tool, is used to intercept and display packets transmitted/received on a network.Tcpdump command provide various options like dumping the tcp packets only,udp packets only,packets from a specific ports, dumping traffic of a specific interface(This is very useful when you have multiple interfaces connected to different network) and many more.Some of important examples are: tcpdump -q : It displays the quick output. tcpdump -i eth1: It displays the traffic of eth1 interface. tcpdump udp: It captures the udp traffic tcpdump port : It captures the traffic of a particular port number. tcpdump -w xyz.log: It send the captured packets to a file xyz.log. tcpdump "tcp and !www.xyz.com": It captures the tcp packets except from www.xyz.com 2.nmap: nmap,Network mapper, is a opensource utility for network exploration.nmap dis...

Download your songs from websites with wget and flashgot utilities. Wget is inbuilt utility in Linux and can be used in windows system just downloading wget for windows.use the following link to download the wget for windows: http://www.brothersoft.com/wget-for-windows-download-5755.html In linux, use wget in command line to download single as well as bulk songs.Follow the below example as shown in screenshot for doing the same: Alternatively, download your songs just adding a mozilla firefox addon "flashgot".Here are the steps to download songs using flashgot. (1)Open the url https://addons.mozilla.org/en-US/firefox/addon/220 and click on "Add to Firefox" button. (2)Click on Install now once software installation window pops up. (3) Restart the firefox once installation is successful. (4) Open the website you want to download the songs from and select the song you want to download.example youtube.com (5)Navigate to Tools->Flashgot and click on Flashgot Media...

To implement the integration of virtual network in GNS with the external physical network, I created a virtual topology using Cisco routers as shown in the diagram below: In my experiment above, i've selected 10.10.10.0/24 network and subneted  into small networks each accommodating only two usable IP addresses. The topology shown above is configured and network within the GNS is working fine i.e ping among each node work correctly.        Now, let's jump into the main point of this blog post. Can we connect this virtual network in GNS with the real external network? Can we pass the real traffic from our servers/computers located in different subnet through this GNS topology? The answer is yes, we can. And yes, ideally to the second problem, the computer should have two NIC cards. One is connected to X network & the other is connected to the Y network. Let's say you've a few servers which are located in 192.168.112.0/24 subnet and others are lo...

Recently, I needed to use some advanced features of the Cisco IOS-XR router within the GNS topology. However, GNS doesn't have any ASR 9k series router and also, getting the IOS-XR iso/bin image is very difficult. I decided to use IOS-XRv software to emulate the VM in Oracle virtual box. However, the implementation drove me nuts. It ain't so easy as it looks. Here are the proper steps which ensure IOS-XR router emulation without any issues.   To emulate cisco asr9k router in VirtualBox for GNS, follow these steps: Download  asr9k ova image from the link: https://upload.cisco.com/cgi-bin/swc/fileexg/main.cgi?CONTYPES=Cisco-IOS-XRv.  You need to provide Cisco credentials (or register if not present) Install & configure VirtualBox, follow the link:  http://www.if-not-true-then-false.com/2010/install-virtualbox-with-yum-on-fedora-centos-red-hat-rhel/comment-page-3/ Alternatively, follow these two steps: Download VirtualBox rpm:   wget  http:...