Yesterday after more than a year's delay my zBC12 mainframe finally booted up. This is a machine that was donated to me in hopes to advance the hobbyist community, which I am eternally grateful for. Image 1: Athena, the zBC12 that just now got online Then what is the main selling point of the zBC12 versus the z114? You might recall my article System z on contemporary zLinux where I explained that running modern Linux on a z114 is hard. This is the main selling point for me to upgrade - being able to run things like more modern Linuxes than z114. While the latest OSes in zLinux, z/VM, and z/OS require z13 or newer - a zBC12 still allows me to run a few releases newer software. Image 2: The operator himself in the picture with Athena Perhaps one of the bigger deals that is very welcome is the support for OSA-Express5S. This means that while previously you needed both PCIe and I/O bays in order to have both effective higher speed connectivity like 8G FC or 10 GB Ethernet as well as
In this post I want to dig deeper into a phenomenon that I spent a few day debugging with friends. It will be a story of a behavior that seems illogical at first glance, broken even, but will seem feasible in the end. Let's begin! Things you will need: The scenario requires one host and one switch minimum*. In our example we will use two Linux hosts, an Arista DCS-7050S switch, and an Arista DCS-7050QX switch. The second switch and host is not strictly needed, but it makes the scenario more realistic and is how we found this issue. The story begins with you and a couple of friends are building an internet exchange (IX) for education and for fun. The simplest IX is just a simple switch - yes even an unmanaged thing you can pick up for $10 would work theoretically. The switch has one purpose: connect different actors together so they can route traffic between each other. See diagram 1. Diagram 1: Your typical IX network. It's just a switch. You have your IX switch and you have y