When using Linux you’ll come to use a certain group of tools daily. In your tool bag you’ll no doubt have a worn grep, a shiny sed, a beat up awk, and a collection of other well used tools. One of my personal favourites is find. Find allows us to pinpoint a specific file by name, or by a certain characteristic. We can link these search options together to work with very granular patterns to match against.

Though Linux is usually thought of as a server OS. It has huge amount of other implementations from embedded systems, the world of IOT, the mobile phone sector, and we’re all still waiting for the year of the Linux Desktop(sure it’ll be this year). But a function that is often over looked is the available routing protocol suite that eanbles linux to function as a router. The routing protocol suite started off as a project called Zebra, which after becoming discontinued morphed into Quagga Routing Software.

Generic Routing Encapsulation(GRE) tunnels are a technology that was developed by Cisco but, is now an open standard through RFC 2784. GRE tunnels can provide use with a lot of versatility when needing to move different protocols between networks. Though we have now moved into an era that is predominantly TCP/IP, when GRE was developed it was at a time of multiple network technologies, IPX, Appletalk, Token Ring, etc, flourished. GRE provided the ability to encapsulate these technologies and let them traverse an Internet Protocol network.

In my previous post I worked through how to use EEM when we had the constraint, of having to keep the Backup circuit interface shutdown when not in use. Without this constraint we can implement redundancy with just Administrative Distance. Administratvie Distance This is a metric that is used by vendors to rate the reliability of a route. Vendors do use different metrics. I’ll be using Cisco devices in this example.