How Does Internet Work

I just passed the AWS Advanced Networking Specialty

Valter Popeskic — Thu, 08 Jan 2026 05:59:59 +0000

It’s been almost exactly 11 years since I passed the R&S CCIE lab in Brussels, and now it was time to go with something more cloudy 🙂 I just passed the AWS Advanced Networking Specialty, and unlike CCIE I did this one on my first attempt. This blog has been running for 16 years now. While the last few years have been quiet here, my professional life has been anything but. I’ve transitioned from a CCIE-focused, Cisco datacenter role into a fast-paced, startup-like environment. My focus has shifted from building physical cloud underlays to designing automated, high-performance cloud-native architectures. Recently,

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Cisco Champion 8th year in a row

Valter Popeskic — Wed, 09 Apr 2025 11:42:32 +0000

Just got the news—I’ve been selected as a Cisco Champion for the 8th year in a row! Truly honored and thankful to be part of such an inspiring community. This year is full of milestones. While Cisco celebrates its 40th birthday, I’m marking 10 years as a CCIE and 15 years from my CCNA—a journey that’s brought endless learning, challenges, and growth throughout my career. Being a Cisco Champion year after year has been a great way to stay connected with amazing people, share knowledge, and keep up with the ever-evolving tech world. Here’s to Cisco’s 40 years of networking—and

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Google Jupiter Data Center Network Fabric – New Way of Building Data Center Network Underlay

Valter Popeskic — Sat, 17 Sep 2022 10:51:47 +0000

Google’s Datacenter Optical Circuit Switches and Jupiter network fabric Google’s data centers are unlike any other. It seems they have windows like normal houses because as from the last SIGCOMM’22 presentation, they took their SPINE switches and threw them right out of that window. Google worked on the Micro Electro Mechanical Systems (MEMS) for years in order to build an Optical Circuit Switch (OCS) that would enable dynamic reconfiguration of optical connections between switches in the data center. Optical Circuit Switch enables on-the-fly data center fabric aggregation block switch connections reconfiguration without the need for physical rewiring. And most interestingly, the

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Cisco DNA Upgrade Issues – Application Update Stuck

Valter Popeskic — Wed, 08 Jun 2022 12:41:43 +0000

After initiating Cisco DNA Appliance version 2.1.2.4 and starting an upgrade towards 2.2.2.8 in order to get to 2.2.3.5 I got a strange issue where the appliance system update went fine but the switch to 2.2.2.8 was disabled until Application Updates did not finish. The real issue here was that Application Updates of Cloud Connectivity – Data Hub got stuck on 12% for 4 days without timing out or finishing. Tried several appliance reboots from CIMC which didn’t help. Below are the steps that helped sort out Application Updates issues with container pods being stuck at the point of pooling

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Cisco Catalyst Stack Upgrade

Valter Popeskic — Sun, 08 May 2022 03:55:07 +0000

Well… It will reboot your whole switch stack at once, In case you were wondering. But it has a neat feature of automatic rollback to the previous IOS XE version if something goes south with the newly upgraded switches. The same goes for non-stacked Cisco Catalyst C9200 and C9300 switches, but the question was, and the answer is hard to find if the stack would reload members sequentially or it would just reload all members at once. The answer is of course the least good option which makes the upgrade impossible without network outage even if other devices are connected

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TOP 25 in Cisco IT Blog Awards

Valter Popeskic — Tue, 15 Mar 2022 10:29:01 +0000

It was a year of big changes in every way. I was fortunate enough to be surrounded by great professionals working on huge projects and then even to get the chance to switch to some completely new technologies that I never really worked with before. It was great, it is still very intense and from my perspective, all changes were for the better. But as with all periods with a lot of action, all those draft articles on this blog’s queue didn’t yield as much new material as I wanted. It was a year of almost no writing but a

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Switch vSphere Enterprise Plus license to vSphere Standard on a NSX-T enabled cluster

Valter Popeskic — Wed, 15 Dec 2021 06:51:05 +0000

This article describes the strange workaround of switching VMware NSX-T enabled cluster from using vSphere Enterprise Plus license to vSphere Standard license with vDS licensed through NSX-T. I really hope that you will not need to go through this as it is quite like bringing the whole environment up from scratch. But if you have two clusters with enough resources it will enable you to do it without downtime. Environment on which this was tested is vSphere 7.0.2 and NSX-T 3.1.2 NSX-T as a network and security platform enables network functions to be virtualised on your vSphere cluster. The way

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Missing good old ‘wr’ command on N9K? let’s bring it back!

Valter Popeskic — Fri, 15 Oct 2021 05:58:00 +0000

Doing a lot on Nexus 9000 series datacenter boxes (N9K) lately? Sure you’re missing the good old ‘wr’ command to save your last startup-config into running-config. NXOS architecture guys decided that you should be really well concentrated when deciding to save your nice new configuration to survive device reboot and type: N9K_1(config)# copy running-config startup-config. Just typing ‘wr’ into the console would be too nice right? Let’s use the alias configuration and bring that command back to the box. N9K_1(config)# copy running-config startup-config 100% Copy complete, now saving to disk (please wait)... Copy complete. N9K_1(config)# If you try ‘wr’:

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NSX-T Edge Transport Node Packet Capture

Valter Popeskic — Thu, 30 Sep 2021 10:35:20 +0000

NSX-T v3.0.1 and v3.1.3 were used to try the stuff described below As always with network engineers, even when working with SDN/SSDC solutions, sooner or later you will be asked to troubleshoot connectivity across your hops. And if working with VMware NSX-T platform, your next-hop for the North-South Datacenter traffic will almost always be NSX-T EDGE Transport Node VM. It will be really useful then to be able to get some packet traces out of that box in order to troubleshoot the traffic issues in detail. One of the examples would be simple routing or some sort of Loadbalancing traffic

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VMware NSX-T Install Tips & Tricks

Valter Popeskic — Wed, 23 Dec 2020 07:27:06 +0000

Intro It’s a shortlist of things that you should probably know when installing VMware NSX-T. Of course, installing NSX-T should be done by following the official documentation. This here is just a few additional points that could help. It’s for your peace of mind afterward. This is an article from the VMware from Scratch series NSX Manager is a Cluster of three VMs You should end up having three NSX-Manager VMs in a cluster when you finish NSX-T installation. The first one will be deployed via .ovf file from vCenter, the other two direct from first NSX Manager GUI as

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VMware TKGI – Deployment of Harbor Container Registry fails with error

Valter Popeskic — Fri, 11 Dec 2020 11:15:14 +0000

This is an article from the VMware from Scratch series During the process of preparation to Install Tanzu Kubernetes Grid Integrated Edition (TKGI v1.8) on vSphere with NSX-T Data Center (v3.0.2) one of the steps is to use Ops Manager to deploy Harbor Container Registry (in this case v2.1.0). The process of deployment ended with Harbor error several times so I’m sharing here my solution in order to ease things out for you giving the fact that I didn’t come across any solution googling around. In the process, the Harbor Registry product tile is downloaded from the VMware Tanzu network portal, imported

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New ACI deployment? Watch out when connecting APICs to Leafs

Valter Popeskic — Sun, 27 Sep 2020 06:35:52 +0000

It’s one of those articles aimed at the people with Cisco ACI experience who don’t bother with reading all the install and other guides again while going through n’th time of building and ACI fabric, like me. When it comes to Cisco ACI, you really should. There’s a small change with the physical build of the third generation of APIC server where 10G SFP interfaces from APIC towards the Leaf switches (used for fabric discovery and later for the in-band controller to fabric communication) where 4x10G card is built in the server and not like 2x10G on M2/L2 and other

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Software-defined data center and what’s the way to do it

Valter Popeskic — Mon, 10 Feb 2020 13:59:28 +0000

SDDC – Software-Defined Data Centers Times of Software Defined everything has long since arrived, the need to implement many appliances, two or more for each network function, is not so popular anymore. The possibility to manage packet forwarding, load balancing and security of network traffic inside the datacenter from one simple web console is showing finally that things can be managed in a simpler way after all. All vendors in the networking world tried to come up with their own way of centralizing data center management, as it ends up, all of them did it, some better than the others.

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Cisco Champion for 2020

Valter Popeskic — Tue, 04 Feb 2020 09:42:22 +0000

I made it to the list of Cisco Champions for 2020 which is now the third year in a row! The primary reason I could again be selected between the first 100 Cisco champs for 2020 in the early acceptance process is the stuff that I shared through this blog and because of the contact with people that got to me directly via my blog comments or e-mail. Again, 2019 was another year full of great projects and big challenges with new technologies. We finally break the barrier of NFV and Automation and got some great stuff done using

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Best Analysis Finalist – Cisco IT Blog Awards for 2019

Valter Popeskic — Mon, 25 Nov 2019 12:58:36 +0000

This blog was selected as a finalist in Cisco BLOG Awards in the Best Analysis category, the category for resources that provide insightful discussions and help for networking architects around the world. Fancy right? Do you agree? Go and vote, hit the big green button it’s the second one on the list 😉 https://www.ciscofeedback.vovici.com/se/705E3ECD18791A68

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Cisco ACI – API Calls vs JSON POST

Valter Popeskic — Tue, 24 Sep 2019 12:55:48 +0000

API Calls method The fancy way of configuring Cisco ACI Fabric is by using Python script for generating API calls. Those API calls are then used to configure Cisco ACI by pushing those calls to APIC controller using POSTMAN (or similar tool). Configuration changes done this way are those that you are doing often and without much chance of making mistakes. You write a Python script and that script will take your configuration variables and generate API call that will configure the system quickly and correctly every time. The thing is that you need to take the API call example

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Cisco ACI – Configuring by POSTing JSON

Valter Popeskic — Mon, 23 Sep 2019 11:34:18 +0000

If you are configuring Cisco ACI datacenter fabric it will sooner or later get to the point that you need to configure multiple objects inside the GUI which will, by using the click-n-click method, take a huge amount of time. While using POSTMAN to create multiple objects of the same type is the preferred method that everybody is speaking about (because you can generate REST API calls using Python or something similar), the quickest way to do it is using POST of JSON configuration file directly through the GUI. POSTing JSON config example As described above, the POST of JSON

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Juniper SRX Cluster Failover Tuning

Valter Popeskic — Tue, 27 Aug 2019 11:11:47 +0000

If you check Juniper configuration guide for SRX firewall clustering, there will be a default example of redundancy-group weight values which are fine if you have one Uplink towards outside and multiple inside interfaces on that firewall. set chassis cluster redundancy-group 0 node 0 priority 100 set chassis cluster redundancy-group 0 node 1 priority 1 set chassis cluster redundancy-group 1 node 0 priority 100 set chassis cluster redundancy-group 1 node 1 priority 1 set chassis cluster redundancy-group 1 interface-monitor ge-0/0/5 weight 255 set chassis cluster redundancy-group 1 interface-monitor ge-0/0/4 weight 255 set chassis cluster redundancy-group 1 interface-monitor ge-5/0/5 weight 255

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Configuring MACsec Encryption

Valter Popeskic — Thu, 11 Jul 2019 09:39:04 +0000

This article describes the simplest way to enable MACSec using preconfigured static key-string. The example was tried on Catalyst 3850 and should work on other switches too. There is another article that I wrote years ago which describes a more complex implementation with dot1x etc. MACSec Media Access Control Security is the way to secure point-to-point Ethernet links by implementing data integrity check and encryption of Ethernet frame. When you configure MACsec on a switch interface (and of course, on the other switch connected to that interface), all traffic going through the link is secured using data integrity checks and encryption.

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How to Advertise a Route from ACI Layer2 BD Outside the Fabric?

Valter Popeskic — Wed, 17 Apr 2019 04:41:20 +0000

Sometimes you will have some L2 domains (Bridge Domains – BD) in your datacenter that will be used with hardware appliances like F5 NLB or something like an additional firewall, WAF or something similar. That is the case where ACI will not route or bridge but the only L3 point of exit from that kind of segment would be on actual hardware appliance outside ACI Fabric – connected to the Leaf port. We will take an example here and use it throughout the article where BIG IP F5 NLB is used as an L3 termination of L2 BD 10.10.10.0/24. F5

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ACI MultiPod – Enable Standby APIC

Valter Popeskic — Mon, 08 Apr 2019 11:29:12 +0000

APIC Controller Cluster You actually need three APIC controller servers to get the cluster up and running in complete and redundant ACI system. You can actually work with only two APICs and you will still have a cluster quorum and will be able to change ACI Fabric configuration. Loosing One Site In the MultiPod, those three controllers need to be distributed so that one of them is placed in the secondary site. The idea is that you still have a chance to keep your configuration on one remaining APIC while losing completely primary site with two APICs. On the other

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Setting up Cisco ACI From Scratch

Valter Popeskic — Tue, 12 Mar 2019 05:39:11 +0000

ACI from cabling, APIC initialization, fabric discovery to fabric policy creation and first Application Policy configuration in one place.

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ACI MultiPod and how to build MultiDatacenter with Cisco ACI

Valter Popeskic — Thu, 28 Feb 2019 14:15:55 +0000

What is MultiPod? ACI MultiPod was first designed to enable the spread of ACI Fabric inside a building (into two or more Pods), let’s say in two rooms at different floors, without the need to connect all the Leafs from one room to all the Spines in the other room. It was a way of simplifying the cabling and all that comes with building spread CLOS topology fabric stuff. MultiPod also saves some Leaf ports giving the fact that Pod to Pod connection through Multicast enabled IPN network connects directly to Spines. People soon realized that MultiPod will be a great solution

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What is Cisco ACI?

Valter Popeskic — Sun, 13 Jan 2019 08:00:09 +0000

Hello World This is an overview of what I think Cisco ACI actually is. It uses some examples from the lab environment to show you how the things look like when you start to work with ACI. There are other articles in the works which will be online soon and which will go in details through the real configuration of ACI and best practices while doing it. What is this Cisco ACI Fabric? Cisco ACI is a datacenter network Fabric. It actually means that it is a networking system of more networking L3 switches that have a modified, next-generation OS

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CLOS Topology

Valter Popeskic — Fri, 11 Jan 2019 11:10:05 +0000

Edson Erwin invented this highly scalable and optimized way of connecting network nodes in the 1930s and Charles Clos made the telephone nodes interconnection design using that solution. It was even before we had IP networks. He invented it in order to optimize the architecture of telephony network systems back then. It was not used in IP based network for last few decades but it experienced a big comeback with new datacenter design in the last few years. It was first invented only for scalability requirements that it solved beautifully. In new datacenter design, CLOS topology of interconnecting network devices scalability

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Cisco Champion for 2019

Valter Popeskic — Thu, 03 Jan 2019 06:44:03 +0000

Again I made it to the list of Cisco Champions, making this the second year in a row! I am so glad that my effort to give back to the community and to all my networking fellows out there paid off again in the shape of this recognition from Cisco. This badge is only a small thing, relating to all the community connections and sharing that my involvement with networking community via social media and this blog, made possible. It only pushes me to get even more done in the future. In 2018 I was involved in a few very challenging new

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BFD – Sub-second Failure Detection

Valter Popeskic — Tue, 11 Sep 2018 12:26:14 +0000

If there’s no BFD If you have two routers directly connected, like here: In this case, it is normal that one of them will remove the routes learned from the other if the other one goes down completely. It is because the link will go to down state and the routing protocol adjacency will disappear. If two routers are connected through an L2 device (switch) like down here: In this case, when one of them goes down, it will not take down the interface of the L3 neighbour (other router) because the switch will still work fine and it will

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MTU and TCP MSS

Valter Popeskic — Fri, 29 Jun 2018 08:40:52 +0000

Intro The largest chunk of bytes that a transport protocol can forward across specific medium is called MTU – Maximum Transmission Unit. If we speak about Ethernet, which is today the most common, he has by default a frame size of 1522 bytes with the payload of 1500 bytes which is the amount of useful data he can carry in a single frame. The story about MTU is that the MTU of specific protocol basically defines how much payload (or highest protocols headers + their payload) it can carry in its biggest packet, not counting his own headers. Putting more

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The New Way of Generating IPv6 – SLAAC EUI-64 Address Format

Valter Popeskic — Thu, 22 Mar 2018 14:05:52 +0000

There was an old way of generating Interface IPv6 address using SLAAC process (Stateless autoconfiguration). You simply configured that you want SLAAC autoconfiguration and the interface IPv6 was generated by squeezing “FFFE” in hex (11111111 11111110 bits) between two parts of physical MAC address of that interface. Then, after a while, several comments came to IETF about the use of predictable Interface Identifiers in IPv6 addresses. They were pointing to the ease of correlation of host activities within the same network and across multiple networks. If Interface Identifiers are constant across networks this is negatively affecting the privacy and security of

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Create or Edit a File on Cisco IOS Flash

Valter Popeskic — Thu, 01 Mar 2018 10:05:31 +0000

There is always the option to edit a file locally on your computer in notepad++ and then upload it to Cisco device. With this trick, you can write or edit a file from Flash memory directly from Cisco IOS console. If you need it for whatever reason, maybe to change something in the config file or something else, this is the way to do it. I was using if for my next article lab where I needed a file on the flash with at least 1600 bytes so I can pull it from neighbouring router with HTTP and check some

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I Became Cisco Champion for 2018

Valter Popeskic — Fri, 19 Jan 2018 05:46:36 +0000

I just received an e-mail from Cisco with the notice that I was elected Cisco Champion for 2018. As Cisco says: “Cisco Champions are a group of highly influential technical experts who generously enjoy sharing their knowledge, expertise, and thoughts on the social web and with Cisco. The Cisco Champion program encompasses a diverse set of areas such as Data Center, Internet of Things, Enterprise Networks, Collaboration, and Security. Cisco Champions are located all over the world.” I must say that last 7 years of writing this blog was the primary reason why one should pick me for this flattering

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Link Aggregation – LACP Protocol

Valter Popeskic — Fri, 05 Jan 2018 06:07:10 +0000

EtherChannel enables bundling multiple physical links connecting same devices into a single logical link. I will try to show you how it is configured and how it works. The issue with one uplink I made an example with 8 clients connected to two Cisco 3850 switches. For start, those two switches are connected together with 1G copper on Interface Ge1/23. The clients are also connected to 1G ports. In this case, when all of those four clients on the left side start simultaneously sending traffic at full speed to different computers on the right side, they will congest the uplink

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Check Point Firewall VM Disk Resize

Valter Popeskic — Wed, 29 Nov 2017 12:48:13 +0000

It is related to Check Point MGMT VM with R80.10 in my story, but you would as well want to resize Check Point gateway firewall hardware box or VM. I was searching for a simple solution and found different ones that didn’t work for me, so here are the steps that you need to go through when you resize your CheckPoint VM disk in vCenter and then need to expand the partition inside Check Point VM in order to use the additional space. Of course, you did choose too small HDD for your VM when you created it and now

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Celebrating 6 Years

Valter Popeskic — Wed, 29 Nov 2017 07:05:18 +0000

Last month I celebrated 6 years of writing my blog. This project reached yesterday his most visited day in history with more than 1500 visitors and more than 31K all together in November. Nice to finally see someone actually reading my rumblings. It was and still is hard work of editing old posts making them better and finding new interesting stuff to write about. Blog is about computer network technologies, you know, the stuff that makes thing get to you and appear on your device’s screens so you can stare at it all the time 🙂 Some other interesting trivia:

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IPv6 Generated with EUI-64 Has a Strange Bit Inside

Valter Popeskic — Mon, 30 Oct 2017 16:08:40 +0000

What is universal/local bit in IPv6 EUI-64 address? One of my readers contacted me with an interesting question in comments of “IPv6 – SLAAC EUI-64 Address Format” article. The question was: “How come that the ipv6 address after the prefix is 21C:C4FF:FECF:4ED0 if the mac address is 00-1C-C4-CF-4E-D0?” Of course, we all know from the previous article that EUI-64 process is taking the interface MAC address (if that is an Ethernet interface) and it creates 64 bits Interface ID with it by shimming additional FFFE (16bits in hex) in between the MAC address bits. The reader was confused with an

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MACSec – Media Access Control Security

Valter Popeskic — Thu, 31 Aug 2017 05:44:26 +0000

Media Access Control Security or MACSec is the Layer 2 hop to hop network traffic protection. Just like IPsec protects network layer, and SSL protects application data, MACSec protects traffic at data link layer (Layer 2). MACSec is standardized IEEE 802.1AE hop-by-hop encryption that enables confidentiality and integrity of data at layer 2. It encrypts entire Ethernet packet except Source and Destination MAC addresses on any device-to-device, switch-to-switch, router-to-switch, host-to-switch directly connected wired L2 connection. If we compare MACSec with, for example, IPsec, MACsec provides same security but on layer 2 for each hop separately. On each hop, packets are

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Reflexive Access List

Valter Popeskic — Fri, 12 May 2017 13:00:36 +0000

Some of my readers commented on my old article about reflexive access-list with issues in the configuration. I tried it in the lab again to be sure I didn’t make any mistake in the configuration example and here I’m sharing the lab and the config used. About Reflexive Access Lists Extended ACLs are a special kind of extended access-lists that have limited stateful behaviour technique implemented for TCP sessions. It is better to say that reflexive access-list is simulating stateful behaviour because it, by use of ‘established’ command, is allowing TCP packets that have the ‘ACK’ bit set but not

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Books that I like

Valter Popeskic — Wed, 03 May 2017 13:17:27 +0000

I was planning for some time now to make a list of books I read recently, here’s the list It should be something like a book reading suggestion list in order to maybe help you pick the right materials in your networking technology learning journey. On the top are the books I used most while studying for my certs but also some of them are the books that I usually carry with me on my Kindle or PDF wherever I go. It is always a good idea to have those books on you so you can have a look at

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Juniper Control Plane Protection

Valter Popeskic — Wed, 03 May 2017 06:14:05 +0000

I already wrote about Control Plane Protection in one of my previous posts focused on Cisco device configuration. Here we will make the same thing on Juniper device, I was using Juniper SRX300 and Juniper SRX1500 devices in my lab. CoPP ?? Control Plane Protection (CoPP) is a method of protecting processor unit, running services on your network device, against excessive flooding. Excessive flooding of traffic aimed towards your router/firewall processor, being that valid or malicious, is always undesirable and can also be dangerous. A network device, which starts the receive more control traffic that his processor can process, will

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How to Clear Entire Configuration of your Juniper Device

Valter Popeskic — Thu, 13 Apr 2017 10:39:02 +0000

If you have a Juniper device that needs to be sent to RMA or you are just putting it to some other use on your network, you will probably want to completely clear the configuration on it. There are different ways to do it for different purpose. If you want to securely wipe all data from this device and make it completely like when you received it from the store then next command is the right one to use: root@RSRX> request system zeroize This one will completely wipe your Juniper device and clear configuration together with all data from flash.

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You Know How Networks Work, Want To Know How Everything Else Works? Here’s Some Books

Valter Popeskic — Thu, 16 Mar 2017 13:19:46 +0000

I know, this is not about networking but I received few great feedbacks to my posts about the matter so I decided to share with you the materials I used to write it. It’s not about networking, but it is about everything. QUANTA?! I was writing about quantum cryptography and quantum key distribution process few months ago (which are network related). When I started to write those articles I was not aware that it will take me more that two months to write something close to understandable about quantum world. As it came out, like many times before, I was in

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The Use of Graph Database in Network Complexity Analysis

Valter Popeskic — Fri, 24 Feb 2017 12:22:48 +0000

Computer networks are probably the best example of graphs these days. I started therefore to consider graph database as an excellent tool for storing experimental results of my networking complexity analysis method. It’s a project that I’m doing (starting to do) in which I will try to create a better method of computer network complexity audit by combining few of already existing methods and by additionally enhancing some of their algorithms to get more precise results out of the whole thing. The idea is that most of network complexity measurement mechanism rely strongly on graph theory in which most metrics

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Redistribute Static on Juniper & Cisco

Valter Popeskic — Wed, 22 Feb 2017 14:05:36 +0000

In case you wondered how to redistribute static routes into dynamic routing protocol you are at the right place. This is normally a basic thing to do, but I will let you know how to do it in different ways on different vendor devices so it might be interesting. We will go through few examples of normal static to OSPF redistribution and then see how it can be partially done with only part of static routes using route filters. I’ll do it on Cisco and Juniper devices so we can see what’s the difference. Cisco In Cisco CLI, redistribute static

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Enable Source-Specific Multicast in Iperf

Valter Popeskic — Fri, 30 Dec 2016 06:30:51 +0000

I was preparing lab environment to test configuration of Source-Specific Multicast on Juniper SRX Equipment and needed a tool to generate and measure Source-Specific Multicast streams. I was aware that Iperf is a good enough tool to generate and measure multicast and unicast traffic but support for SSM was missing from current version. Fortunately there are always some developers which are interested in networking so one of them developed a special Iperf version 2.0.5 with SSM support. The idea here is to show how to make this version of Iperf work on your Cent OS or similar Linux machine. Here

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Source-Specific Multicast Configuration

Valter Popeskic — Thu, 29 Dec 2016 08:42:20 +0000

In SSM, Source-Specific Multicast, things are done differently from standard multicast forwarding. SSM is specifying a group of hosts that are receiving same multicast stream using group IP address and additionally using stream unicast source IP. In this article it is shown how to configure Source Specific Multicast on Cisco and Juniper equipment. In standard multicast, forwarding is done using group IP address which is an IP from multicast dedicated range 224.0.0.0/4 (224.0.0.0 – 239.255.255.255) or FF00::/8 in IPv6. Each multicast group IP address is a single address which specifies all hosts receiving a specific stream, streamed towards that group

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QKD – How Quantum Cryptography Key Distribution Works

Valter Popeskic — Thu, 01 Dec 2016 06:13:19 +0000

QKD – Quantum key distribution is the magic part of quantum cryptography. Every other part of this new cryptography mechanism remains the same as in standard cryptography techniques currently used. By using quantum particles which behave under rules of quantum mechanics, keys can be generated and distributed to receiver side in completely safe way. Quantum mechanics principle, which describes the base rule protecting the exchange of keys, is Heisenberg’s Uncertainty Principle. Heisenberg’s Uncertainty Principle states that it is impossible to measure both speed and current position of quantum particles at the same time. It furthermore states that the state of observed particle will change if and

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Unable to access Cisco ASA through AnyConnect VPN?

Valter Popeskic — Sun, 13 Nov 2016 08:58:46 +0000

I stepped on this issue few weeks ago. I was implementing a new ASA Firewall solution, first time for me with software newer than version 8.4.2 It seems that all those stories about changes in the NAT logic after that version were true. This is what I found out about ASA packet processing. Configuration was really straightforward and everything worked fine except one thing. When connected remotely using Cisco AnyConnect I was able to access all devices inside the network (inside ASA firewall), but not the ASA itself. I wasn’t able to connect with SSH nor with ASDM. I, of course,

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Introduction to Quantum Cryptography

Valter Popeskic — Fri, 11 Nov 2016 07:43:09 +0000

Quantum cryptography is a new technique of securing computer network communication channel. Existing standard crypto systems are using advanced algorithms to create key pairs which are extremely hard to inverse engineer. Quantum cryptography avoids any mathematical algorithm and uses principles of quantum physics. Quantum crypto implements a new technique of generating and exchanging crypto keys which makes it impossible for third party entities to get those keys by snooping or to create man in the middle by snooping and sending copies of original key. Keys generated in this way will automatically destroy themselves if read by third-party interferer. When generated between two sides, using quantum key distribution, secret keys will

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Cryptography

Valter Popeskic — Wed, 02 Nov 2016 06:47:48 +0000

If you want to send or store data and be sure it is safe from being intercepted, you will use Cryptography. Cryptography uses chipper as mathematical virtual lock to make data scrambled so that is not understandable if intercepted by unauthorized third parties. There are different cryptography techniques, some of them are: encryption, hashing, and steganography. Cryptography can be differentiated by usage of different key types: Symmetric Key Encryption Asymmetric Key Encryption Symmetric Key Encryption is sometimes known as Secret Key Cryptography. Main characteristic of this type of cryptography is the same key usage in encryption and decryption of transferred

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ICANN and the future of DNS and internet

Valter Popeskic — Wed, 12 Oct 2016 06:42:49 +0000

I’m sorry to put here something that is not really technical but for a blog with the name “howdoesinternetwork.com” it would be strange not to follow the story about the future of DNS governance given the fact that DNS is a crucial part of internet functionality. You probably know how the internet works given the fact that you are visiting a blog like this. Regardless of that, it will not hurt to explain in few words the importance of DNS (Domain Name System) for a normal internet operation. Let’s surf to se how this works If you want to open this webpage

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