In this article I will show you how to deny access to specific websites (domain names) with a normal Cisco ASA firewall. This works on either the older 5500 models or the new 5500-X series devices. The only pre-requisite for the firewall is to run software version 8.4.2 and later. Also, you don’t need to […]
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Last week the whole world, and especially the information security community, has been buzzing around the massive ransomware attacks that infected thousands of computers in hundreds of countries. But how did all started? Many of you know the story, but let’s summarize it once again: NSA had developed some secret exploits that took advantage of […]
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In this post we will discuss DNS Doctoring on Cisco ASA firewalls. This is a useful feature and although it’s very simple to configure, not many people know about it. DNS Doctoring is helpful in the following situation: Assume you have a Web Server connected to a DMZ zone on a Cisco ASA firewall and […]
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The Border Gateway Protocol (BGP) is considered to be the routing protocol of the Internet because it runs between Internet Service Providers (ISPs) to interconnect all Autonomous Systems (AS) comprising the whole internet. Of course the above refers to External BGP (eBGP) which runs between different Autonomous Systems. There is also another “flavor” of BGP […]
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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 […]
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Throughout my professional career in networking I was lucky to work with all Cisco firewall models and therefore I have experienced the “evolution” of every firewall product developed by Cisco. For the SMB/SOHO market, Cisco’s initial offering was the PIX 501, followed by the successful Cisco ASA 5505. The latter came to an End-of-Sale in […]
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A new serious vulnerability was discovered on Cisco ASA devices, called “EXTRABACON”, and was recently patched by Cisco by releasing several software updates for the device. You need to carefully read the following security advisory (CVE-2016-6366) from Cisco and patch your devices as soon as possible. At the end of the article above there is […]
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In this post I have gathered the most useful Cisco ASA Firewall Commands and created a Cheat Sheet list that you can download also as PDF at the end of the article. I have been working with Cisco firewalls since 2000 where we had the legacy PIX models before the introduction of the ASA 5500 […]
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Network infrastructure devices (routers, switches, load balancers, firewalls etc) are among the assets of an enterprise that play an important role in security and thus need to be protected and configured accordingly. Many enterprises focus on protecting their servers, applications, databases etc but they forget about security of network devices which are sometimes installed with […]
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On June 7, 2016, Cisco released the “Cisco Visual Networking Index™ (VNI) Complete Forecast for 2015 to 2020” where several notable internet traffic statistics are predicted by the networking giant. I have summarized the forecast document and presenting you below the most important stats and predictions about Internet traffic, Internet usage etc: Global IP traffic […]
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What if I told you that there are almost 500 practical Cisco networking tutorials waiting for you on a single website that can help you learn hundreds of different networking topics? This resource is NetworkLessons and is probably one of the few online education portals with so many lessons on Cisco technologies, ranging from configuration […]
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This tutorial marks the beginning of a series of network security and penetration testing articles that I will be posting on this website. The purpose of this article is to describe how to perform a simple NMAP scan of an IP range/subnet on a network. There are hundreds of scan options with NMAP but I […]
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In this tutorial I will describe the configuration of an interesting network scenario that I’m sure many of you will find helpful. This scenario is applicable in many real world situations, mainly in small to medium networks. The network scenario is as follows: We have three different internal LAN networks which host user computers and […]
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