Category: Equipment and tools

Cisco VIRL is finally out

Cisco virl logoCisco 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 all the time spent troubleshooting lab issues that were really GNS3 issues.

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Redundant Default Gateway solutions in IPv4 networks

This article is an introduction to different default gateway solutions. Those technologies are enabling devices on IPv4 local subnets to have more than one Default gateway configured or at least some configuration that make them work half the way of ideal redundant solution. Idea behind this article is to be an introduction to a set of articles that will explain different redundancy solutions based on IPv6 technology. Some of those technologies, will be used in future and some of them already existing and suggested to be used from day one on IPv6 implementation.

Default Gateway?!

Redundant default gateway

Default gateway is the next hop address of the device that leads the packets out of the local LAN segment. If there are packets destined to an IP address that is not from local subnet PC will forward those packets usually to router device that will have the information where to forward those packets in order to get them transferred towards the destination.

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Cisco VIRL – Virtual Internet Routing Lab


Cisco VIRL - Virtual Internet Routing Lab2In a world in which every day I hear virtualization at least 50 times it would be very strange that there is some part of our digital environment which is not yet virtualised. Today we can see that almost every piece of our server equipment is going to the cloud hence is being virtualised. That is not a new story, server virtualisation i basically existing for decades now. Todays story is about next step in the virtualization process. There is finally a big desire to do the same thing with networking equipment. That’s obviously the way to go as there are more and more server on one hypervisor or on one cluster in the data centers and that implies that would be too expensive to implement any kind of hardware networking devices for each virtual server instance. And that implies that we are living in a world where switches and routers are more and more becoming part of different virtualisation host kernels or hypervisors.

But now when that virtualization technology is basically a normal way of deploying almost all machines and there is nothing standing in between network devices virtualization and us why there is no way to use that technology and make for us a virtualized modeling tool for network design and troubleshooting to?


Yes, there is GNS3 for years now but to be sincere, I tried to use if for some design and troubleshooting sessions and it is so time-consuming to set everything to work right that is was at the end easier to do it on a piece of paper.

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Find unknown static IP on device

If you work in networking sooner or later there will be a situation where someone will bring you a device that you must connect to your network that was used somewhere else before. That can be something like switch, Fiber channel switch, some security appliance, different controllers etc. In that case this device will often have a static IP address assigned and you will not know whish address that is. In that case you are unable to communicate with the device and if you are connecting it to your network he will have different IP from you subnet. That will make the device unreachable.

You need to find this unknown IP address in some way so you can connect to the device and then change the IP.

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Recovery From Corrupt or Missing Software Image on Cisco device

This is a movie based on a true story. Is the issue you will have sooner or later if you are into networking and managing devices? Perhaps you will manage to upgrade hundreds of devices before you will see this happening but maybe it will be one of the first devices in production environment to go down exactly when you don’t have time for this kind of problem. Better be ready and read next short story about how is possible in very short time to revive a dead device stuck without IOS Software on it.

If you have a corrupt or missing software image on Cisco device this is the thing you should do:

Reset to the factory default using Mode button if you have the Mode button, if your device is not having that button then simply reboot the device and hit break or Esc key to stop the booting process. In this example, again, based on my true story I will take an example with recovering one of standalone Cisco Aironet Wireless Access points. It’s basically the same with all IOS devices and some devices that do not have IOS but some older software and then you want them to upgrade to IOS. It’s for example the situation with one very old Cisco Aironet AP350 device. Let’s go…

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