I Became Cisco Champion for 2018

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 badge.

I’m following some of the most active Cisco Champions on Twitter for years.

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Link Aggregation – LACP Protocol

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 between switches and some traffic will be dropped.

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Check Point Firewall VM Disk Resize

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 you cannot upload some hotfixes or vSEC gateway files to it because you don’t have enough space.

Get to vCenter and shut down the VM.

vCenter VM Shutdown

Get more GB to your VM and power it back up.

vCenter VM HDD Space Increase

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Celebrating 6 Years

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:

  • I have 221 posts published currently.
  • I have also more than 300 drafts that may get published. Some things get old before I get to write them so I just skip those.
  • It takes me approximately 10 to 16 hours to write a post, not counting research and draft creation before starting the final edit.
  • I still use paper and coloured pencils to draw all the schemes used on the blog, same as when making first drafts of my future network designs.
  • My blog is using few banners to be able to pay for itself, so it is earning more or less the money I need to run it.
  • From a technical side, it is a small but optimised Linux VPS build by myself from scratch using some commercially available (and paid) solutions to run fast, load pages flash fast and never go down.

Thanks to all the readers and supporters 😉
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IPv6 Generated with EUI-64 Has a Strange Bit Inside

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 additional change that I did not cover in that article which is called universal/local bit of the IPv6 address Interface ID part.

Let’s go.

IPv6 address is 128 bit. First ‘n’ bits (first 64 bits of EUI-64 created IPv6 address) are called “subnet prefix” and the other half of bits are called “Interface ID”.

If we use EUI-64 process to generate a unique IPv6 address of the interface, then we are generating Interface ID from MAC address (or some other kind of L2 address if this is not about Ethernet).

|                     n bits                     |   128-n bits   |
+------------------------------------------------+----------------+
|                  subnet prefix                 |  interface ID  |
+------------------------------------------------+----------------+

On RFC 2373 page 18 chapter: “APPENDIX A : Creating EUI-64 based Interface Identifiers”, you can find that 7th bit on Interface ID part of an IPv6 address (the last 64 bits) is called “universal/local bit”.

If this bit is set to “0” it indicates local scope IPv6 address and if it is “1” then the generated IPv6 address has global scope (it is globally unique).

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