Kerberos Basics

Kerberos is an authentication technology, if you’ve used Microsoft Windows and Active Directory (AD) you will have heard of Kerberos as its the authentication method used to secure an AD Domain and any hosts and devices that are joined to it. I’d like to provide a fairly high-level run through of how Kerberos works, so … Read more

Extreme Networks X695 to Dell S5148F-ON Switch – 10Gbit SFP+ Intermittent CRC Errors

I recently came across an odd problem with the links from our Extreme Networks X695 switches to some Dell S5148F-ON switches, the X695 was running: 30.7.2.1, the Dell switch 10.4.3.6C1. Essentially what started the oddity was a transceiver failure. The equipment has been in production for a few months, all was working well. Suddenly a … Read more

Simple Nmap Ping Scan Example

NMAP (Network Mapper) is a great tool for scanning a network for hosts and devices. I’m going to write a more in-depth article soon, but for now here is a good command that can be used to scan your network (with a ping scan). By default Nmap will perform a reverse DNS lookup on the … Read more

Microsoft Active Directory Trusts Explained

Microsoft Active Directory uses the concepts of “domains”, a domain is the outer edge of a security compartment; within a domain, user accounts, computer accounts and resources are authenticated and share a common authentication source. There is also the concept of a “forest”, a forest is a collection of domains, in the most basic configuration … Read more

Extreme Networks Port Partitioning

The QSFP+ or QSFP28 ports of the Extreme Networks switches can be partitioned, what this means is you can make a 40Gbit QSFP+ port appear as 4 x 10Gbit SFP+ ports, however you’re require a suitable QSFP+ module for example with MTP port and a fan-out cable to split that MTP into 4 x LC … Read more

OSI Model (7 Layers)

The OSI Model (Open Systems Interconnection) model is a set of rules and requirements to model and conceptualise the communication between two (network) systems. Yes, its theory, but in computing and networking it can be useful to use as a basic guide when troubleshooting. It helps you to rule-in or rule-out where a problem might … Read more