I should have written this article from the very beginning of starting this blog because it is one of the most fundamental configuration steps for managing a Cisco networking device (router, switch, firewall etc). Disabling Telnet and enabling SSH on a networking device is also a step forward in increasing security in the whole network. […]
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Although this is a Cisco networks dedicated blog, I decided to start a series of tutorial posts about a general technology which is not directly related to Cisco but it is a field in which Cisco is again a major player. This is IP Telephony and Voice over IP (VoIP). Image Source The two terms, […]
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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 […]
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In this article we will discuss the similarities and differences between the 3 “First Hop Redundancy” protocols supported by Cisco devices. These are Hot Standby Router Protocol (HSRP), Virtual Router Redundancy Protocol (VRRP) and Gateway Load Balancing Protocol (GLBP). The main purpose of the above protocols is to provide redundancy to the default gateway (router […]
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QUIC (Quick UDP Internet Connections) is a new generation Internet protocol that speeds online web applications that are susceptible to delay, such as searching, video streaming etc., by reducing the round-trip time (RTT) needed to connect to a server. By replacing TCP with UDP and encrypting most of its payload, QUIC reduces the time it […]
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As a network security engineer, among tens of other tasks, I run also security assessment and penetration testing projects. One of the most popular and widely used network scanning tool is NMAP. This is one of the tools that I use at the beginning of a penetration testing engagement and helps tremendously in identifying targets, […]
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On October 16, 2017 a serious security vulnerability has been published by researchers from KU Leuven, a university in Belgium. This has to do with WPA2 protection in WiFi networks, which is the modern security standard considered to be very safe so far. This vulnerability has to do with the WPA2 technology itself and is […]
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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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