LSA issue @ January 19, 2017 at 10:43AM

Here is the question: if Host A wants to transmit some data across TCP/IP network to Host B with IP address of how will this Dest_IP address be represented?

Correct, it will be hex encoded, but will the bytestream be like 0x01 02 03 04 or 0x04 03 02 01? Yep, you see where I am going, its endianness who is telling us which byte comes first.

So take a look at this short article which is a perfect read on Endianness. It uncovers why x86 CPUs (back in 90-00's) were a bad choice for networking equipment and how the hell Gulliver's Travels has mixed up with all of it?

#Article #TCP
By: via LSA


Yang Explorer in a Docker container


I would like to see a day come true where all major vendors’ boxes (even small & cheap ones) will be 100% covered by YANG models. Can’t say I believe that it is possible for IETF to standard all the things in vendors domain, but we will manage as long as vendors will stick to standard YANG in their own in-house data modes.

Being in shadows for quite some time, Netconf/Yang are still something new to explore for many of network engineers, myself included. And that’s todays topic — exploring YANG data models with Yang Explorer tool in a docker container (reads: without pain).


LSA issue @ January 1, 2017 at 02:13PM

Hey there, engineers! Its January 1st 2017 and we are happy to welcome you and wish you all the best.
But is it 2017 indeed? How would one tell if his clock is good, if its in sync with the world clock? Yeah, you got it, in the era of the leap second and New Year eve what topic could we bring up if not NTP?

Lucky us, an Australian SRE@Canonical Paul Gear wrote a 5-post long topic called ""The School for Sysadmins Who Can’t Timesync Good and Wanna Learn To Do Other Stuff Good Too"". We bet you'll become grandmaster of NTP once you read all five of them!

#Article #NTP #Synchronization

Part 1 — The problem with NTP:

Part 2 — How NTP works:

Part 3 — NTP install and configure:

Part 4 — Monitoring and Troubleshooting:

Part 5 — Myths, misconception and best practices:
By: via LSA


brvirt: when brctl meets virsh


Hypervisors diversity is definitely one of the benefits of having Nuage managing your next-generation network. That means that we, as Nuage engineers, have to play with all kinds of hypervisors — like KVM, ESXi and Hyper-V to be more precise. As to me, I love to work with KVM most, simply because it gives you that feel that you are in control and can fine-tune or troubleshoot with granularity you want. Thanks to opensource tools like tcpdump, virsh, ss, top, brctl and many many others!

But these tools won’t fit perfectly for every situation every time. For example consider a simple case of a Linux host with a bunch of VMs connected via Linux bridges and answer a simple question: how to determine what VM names correspond to what virtual network interfaces connected to what bridges? I have to say that this question arises quite often when you troubleshoot network connectivity between VMs or gathering network stats.

And the answer to this question can not be provided with above mentioned tools without some scripting. Indeed, in this post I will share a script called brvirt which does the job by combining iproute2 and virsh outputs.

Link: Github repo.


Using free Yandex DNS service in an automated way


This DNS story started when I bought a domain with a specific need — to dynamically create and delete DNS records for Nuage Networks components we use during Proof Of Concepts and customers trials.

Earlier I used to rely on Dynamic DNS services (i.e. whenever I needed a DNS name for my public endpoints. But this approach has two drawbacks:

  1. To use if for free you have to manually prolong you hostname once in a month. Drove me mad every time!
  2. In PoCs/trials you want your domain represent your product. Using in front of a customer is not something that speaks well for your product. And we all know that devil is in the details.

Therefore I decided to buy a domain that will represent a product we are offering and park it to some provider which offers robustfree and API-enabled DNS service. Google cloud DNS and DynDNS while being both cheap are not free. So I kept looking and ended up with Yandex DNS which has all three traits I was looking for. Lastly I automated this DNS workflow so everyone in my team could provision their own DNS entries via one shared tool.

You got it right, in this post I am going to tell you about a completely free DNS service from Yandex with a decent API you can use for your personal needs. And yes, this post is accompanied with a python script which leverages API and automates DNS records provisioning.


LSA issue @ December 13, 2016 at 10:24AM

Here is your fresh IPv6 fix: Tenth iNOG, namely iNOG::A, is all about IPv6 experience.
Technical talks are:
1) Orla McGann (HEAnet) An Irish IPv6 Fairytale
2) Nathalie Trenaman (RIPE) The Sad Tale of 462 Operators Who Switched Off IPv6* (*with a happy ending)
3) Ed Horley (Groupware Technology) IPv6 Operating Challenges

Particulary interesting talk was given by Nathalie from RIPE who was talking about IPv6 global perception seen from RIPE point-of-view.

#Video #iNOG #IPv6
By: via LSA


LSA issue #December 9, 2016 at 02:27PM

There is a popular saying that you don't need to be a programmer to automate your network. Might be true, though you definitely won't succeed in automation tasks without basic Regular Expressions knowledge, that you should take for granted.
Sad thing that regular expressions are not an easy nut to crack, and with this post we would like to share with you useful resources that will help you meet and greet RegExps!

#TipsTricks #Programming — Mastering Regular Expressions, 3rd Edition. — a free and massive tutorial on RegExps — regexps collection for different tasks — the best online regexp engine to test and validate your regexps — solving regexps just for fun — book a place on your desk to hang this RE cheatsheet
By: via LSA


BGP VPLS explained (Nokia & Juniper)


It may very well be that VPLS days are numbered and EVPN is to blame. Nevertheless, it would be naive to expect VPLS extinction in the near future. With all its shortcomings VPLS is still very well standardized, interop-proven and has a huge footprint in MPLS networks of various scale.

In this post I will cover theory and configuration parts for one particular flavor of VPLS signalling — BGP VPLS (aka Kompella VPLS) defined in RFC4761. I’ll start with simple single home VPLS scenario while multi-homing techniques and some advanced configurations will appear in separate post later.

In this topic the following SW releases were used:


Basic IPv6 configuration for Nokia and Juniper routers

This is a quick IPv6 interface configuration tutorial for Nokia 7750 VSR (SROS) and Juniper vMX routers.


Using guestfish to modify VM disk image

EarIier I wrote about some ways to modify VM disk images used by Unetlab. Basically it boils down to running a VM, console to it and change things through its shell. Obviously, this approach is no way near a handy way to do small changes like:

  • loading basic config
  • adding license files

In this post I will talk about guestfish utility which is a part of libguestfs tools set. With guestfish one could easily get a shell-like access to the filesystem located on a disk image (qcow2, vmdk, iso and many others). That is how authors of libguestfs tools describe it:

libguestfs is a set of tools for accessing and modifying virtual machine (VM) disk images. You can use this for viewing and editing files inside guests, scripting changes to VMs, monitoring disk used/free statistics, creating guests, P2V, V2V, performing backups, cloning VMs, building VMs, formatting disks, resizing disks, and much more.

libguestfs can access almost any disk image imaginable. It can do it securely — without needing root and with multiple layers of defence against rogue disk images. It can access disk images on remote machines or on CDs/USB sticks. It can access proprietary systems like VMware and Hyper-V.

To demonstrate the way how guestfish works I will solve a particular task of adding a license file to Nokia (Alcatel-Lucent) 7750 Virtual Service Router (VSR) by embedding it to the disk image itself. Tune in!