How does Internet work - We know what is networking
This article it’s not about mathematics, don’t be afraid. I’m running a networking blog and it’s not my intention to speak or write about anything related to mathematics. Biggest math problem that I’ve done in last few years is some simple subneting, EIGRP metric calculation and that is where I stopped with math for now. On the other hand I love the theory behind algorithms, specially if the algorithm is used in networking and if it is so simple and powerful as Nagle’s algorithm. You can guess, John Nagle is the name of the fellow who created the algorithm. He
How does Internet work - We know what is networking
I found differed kinds of explanations about what that Proxy ARP is all about. After going through all of them this explanation came out. It is fairly simple technique for nodes to get MAC address of a destination host that is on the same subnet but behind a router. It’s a technique that enables our R7 router on the image below to proxy ARP request from C1 computer which tries to find MAC address of computer C3. You need to note that C1 has address from /16 range and that is why it thinks that 192.168.50.50 is the same subnet as
How does Internet work - We know what is networking
This is really cool feature on Cisco router not usually mentioned until you dig a little deeper inside Cisco IOS. But first a bit of theory… What is TCP SYN flood attack TCP 3-way handshake SYN flood DoS attack happens when many sources start to send a flood of TCP SYN packets usually with fake source IP. This attack uses TCP 3-way handshake to reserve all server available resources with fake SYN requests thus not allowing legitimate users to establish connection to the server. SYN packet is the first step in TCP 3-way handshake where client sends connection synchronization request
How does Internet work - We know what is networking
Network Packet Generator or Network Traffic Generator is a tool every network engineer will sooner or later want to use. Here’s one I found and it’s great! First time I saw an Ethernet frame in details on my CCNA class back in 2010 I immediately got the idea about generating some packets on my own. It was logical next step to ask myself: “Ok, so how can I make one of those and see what happens when I send it out on the network?”. I was not really sure that there is a tool that would make it possible. Don’t get me wrong,
How to generate network packets – Ostinato Packet/Traffic Generator
How does Internet work - We know what is networking
Flowing text is a project done as a part of academic work that I am involved with for last few years at the University of Rijeka – Department of Informatics. It’s a short overview at latest achievements in the field of network automation with some lab experiments done to test different paths across the network. The work was presented at 6th International Conference on Information Technologies and Information Society (ITIS2014). The scope of ITIS events are the applications of IT, particularly in social sciences. The conference also covers a wider range of topics related to IT and computational modeling and
How does Internet work - We know what is networking
This one is long. Do not be afraid though, I made it just to give you the fastest way to deploy functional dot1x to your company HQ without reading even more documentation and searching for those little timer default settings. I the article prior to this I showed you how to setup your environment with simple dot1x and make it as simple as possible. I will not repeat again the part about setting up Radius Clients on server side, everything else is here once again just more complex. Now is time for a more complex example that will make your implementation
How does Internet work - We know what is networking
If your LAN is extending to some places where unauthorised people can just plug in and gain access to your protected network, it’s time to implement some security on your access switch. The best thing to do is to implement IEEE 802.1X port-based authentication which will enable users/machine authentication and prevent unauthorized devices from getting access switch port running when connected. IEEE 802.1X port-based authentication is mostly called simply as dot1x. In this article I will show you how to configure some basic dot1x stuff on switch side. I will also include Windows machine side of configuration as this is something most people presume
How does Internet work - We know what is networking
Please note: This has nothing to do with networking in particular! Not if you look from only one perspective. If you look from totally different perspective, with Cisco ACI and all other SDN solutions, you will probably meet with Python programming language (because you will) and then, somewhere in beginning of Python exploration this is the first question that will cross your mind. Of course, if you think like me! Although not directly related to networking, the question bothered me for some time now and the answer is not only really logical when you read it but it is also
How does Internet work - We know what is networking
Please note: This has nothing to do with networking in particular! Not if you look from only one perspective. If you look from totally different perspective, with Cisco ACI and all other SDN solutions, you will probably meet with Python programming language (because you will) and then, somewhere in beginning of Python exploration this is the first question that will cross your mind. Of course, if you think like me! Although not directly related to networking, the question bothered me for some time now and the answer is not only really logical when you read it but it is also
How does Internet work - We know what is networking
It is fairly common to hear about switch being non-blocking. It’s because almost all switches today are non-blocking. But what that means? When I asked people around me on what exactly non-blocking switch means, they were unable to get to the same conclusion. I was going through a lot of different internet places and vendor documents before I wrote this here, but, do not hesitate to add something in comments if you have different view on the subject. Line-rate switch means the same as if you would said wire-speed switch. It basically means that this switch has the forwarding capacity that supports concurrently
How does Internet work - We know what is networking
It is fairly common to hear about switch being non-blocking. It’s because almost all switches today are non-blocking. But what that means? When I asked people around me on what exactly non-blocking switch means, they were unable to get to the same conclusion. I was going through a lot of different internet places and vendor documents before I wrote this here, but, do not hesitate to add something in comments if you have different view on the subject. Line-rate switch means the same as if you would said wire-speed switch. It basically means that this switch has the forwarding capacity that supports concurrently
How does Internet work - We know what is networking
Head-of-line blocking (HOL blocking) in networking is a performance issue that occurs when a bunch of packets is blocked by the first packet in line. It can happen specially in input buffered network switches where out-of-order delivery of packets can occur. A switch can be composed of input buffered ports, output buffered ports and switch fabric. When first-in first-out input buffers are used, only the first received packet is prepared to be forwarded. All packets received afterwards are not forwarded if the first one cannot be forwarded. That is basically what HOL blocking really is.If there’s no HOL blocking happening,
How does Internet work - We know what is networking
Head-of-line blocking (HOL blocking) in networking is a performance issue that occurs when a bunch of packets is blocked by the first packet in line. It can happen specially in input buffered network switches where out-of-order delivery of packets can occur. A switch can be composed of input buffered ports, output buffered ports and switch fabric. When first-in first-out input buffers are used, only the first received packet is prepared to be forwarded. All packets received afterwards are not forwarded if the first one cannot be forwarded. That is basically what HOL blocking really is. If there’s no HOL blocking
How does Internet work - We know what is networking
As this is networking blog I will focus mostly on the usage of CAM and TCAM memory in routers and switches. I will explain TCAM role in router prefix lookup process and switch mac address table lookup. However, when we talk about this specific topic, most of you will ask: how is this memory made from architectural aspect? How it is made in order to have the capability of making lookups faster than any other hardware or software solution? That is the reason for the second part of the article where I will try to explain in short how are the most usual
How does Internet work - We know what is networking
Some time ago I was working on IPv6 implementation and in that period I written an article about NDP (you can read it here). After a while I received some comments that is not written well so I reviewed a huge part of it. It looks my english was far worst two years ago that I was really aware of In the reviewing process I realised that NDP usage of Solicited-Node multicast addresses was not clearly explained. This is the follow-up article which should explain how and why Solicited-Node multicast address are used in NDP. Let’s go! Solicited-node multicast address is IPv6 multicast address used on the local L2
How does Internet work - We know what is networking
Cisco created all sorts of different magic inside their boxes that optimize forwarding processing of packets. Main router function is fairly self-explanatory. Router performs IP forwarding more often called IP routing. IP routing is process of deciding where to send the packet after it was received. IP Routing explained in detail Logic behind IP forwarding is listed in steps here with the assumption it will be an IPv4 packet that was received. This is process switching explained in 11 steps: A frame enters the one of router’s interface First thing that router does is to check frame
How does Internet work - We know what is networking
This is the story on how I became CCIE# 46173 To be honest, when I look back, I do not really know the main reason behind going through all this trouble, but I can tell you the story about how I did it. It’s mostly a thriller, and some drama towards the end. I will give you an overview of the whole process including the materials used, videos watched, books read and struggles that I went through. I think that is the right thing to do. This article is for all of you out there who are still trying to study for this exam and need some suggestions.
How does Internet work - We know what is networking
Cisco finally released long-awaited personal network simulator VIRL. VIRL is a simulator like Cisco CML – Cisco Modelling Lab released few moths ago which is made available for business network simulations and testing in engineering normal day job. With VIRL we got a personal version of CML with drastically lower price tag aimed to help students preparing for Cisco CCNP and more than that for those preparing CCIE lab exam. VIRL will surely help the engineers managing small business network to proof their configuration change before applying it to real network. This solution give us a more stable and “official” GNS3 which will save
How does the internet work - We know what is networking
Few days ago I added an article with Config GNS3 topology for newly published INE Routing and Switching Workbook v5 Full-Scale LAB1. Here’s now the topology with starting config of TS section for LAB1. I will not insert here any of my stories today as the same article was published before but with other topology files so if you would like more info, just go to previous post INE R&Sv5 Workbook Full-Scale Practice Lab1 made in GNS3 DOWNLOAD Everything should work fine in this lab except OSPF Loop-Free Alternate Fast Reroute which is not supported so you will be unable
How does the internet work - We know what is networking
…There’s a nice little pdf to get you through HP is aware that most of networking engineers start their learning process in Cisco Networking Academy. Is is a normal course of events if you want to learn networking. Cisco has the very best study materials and best, carefully developed syllabus that is both high quality […]
When they throw a Cisco guy to do something with HP networking gear