For the following scenario, subnets are stretched across multiple locations using a Layer 2 DCI solution. There are several use cases that require LAN extension between multiple sites, such as Live migration, Health-check probing for HA cluster (heartbeat), Operational Cost containment such as migration of Mainframes, etc. It is assumed that due to long distances between sites, the network services are duplicated and active on each of the sites. This option allows the use of local network services such as default gateways, load balancer’s and security engines distributed across each location, helps reduce server to server communication latency (East-West work flows).
Traditionally, an IP address uses a unique identifier assigned to a specific network entity such as physical system, virtual machine or firewall, default gateway, etc. The routed WAN uses the identifier to also determine the network entity’s location in the IP subnet. When a Virtual Machine migrates from one data center to another, the traditional IP address schema retains its original unique identifier and location, although the physical location has actually changed. As a result, the extended VLAN must share the same subnet so that the TCP/IP parameters of the VM remain the same from site Continue reading
One of the quotes I found in the Mythical Man-Month came from the pre-GPS days: “never go to sea with two chronometers, take one or three”, and it’s amazing the networking industry (and a few others) never got the message.
Read more ...One would think that we're the only ones struggling with Linux CLI (read: bash). Seems like cyber security professionals might be in the same boat according to the nice summary of dozens of Linux/bash commands collected by Robert Graham.
I was recently asked by a friend to read and review a book his publisher had just released. This was a technical book on a topic I was keenly interested in, so I was happy to oblige.
I tackled the book in the way that I normally tackle technical books — a chapter a day, or maybe two chapters in a day. Technical books aren’t recreational fiction for me. I want to grasp the contents of technical books to best make use of the information. This often leads to slow reading. I mull over paragraphs and digest.
This time, I broke that habit. I wanted to get this book done quickly. I wanted the information immediately. I didn’t want to take a few weeks to get through it. Thus, I tried reading the book all at once.
Surprisingly, this worked out well. I ended up getting through the book in four sittings, which perhaps doesn’t sound like “all at once.” Bear with me. The first sitting was a single chapter. The second sitting was a single chapter. Then came the holidays and a complete disruption to my workflow. And then came the epiphany as I stared at the book post-holidays. Continue reading