Tag Archives: routing

How to safely transform a routing domain

As part of my job as a Senior Network Engineer, I develop procedures for undertakings of varying complexity. In this post I’m describing a technique that greatly simplifies any project where a routing domain is expected to churn (i.e. neighborships going up and down, routes flapping), when such event is undesirable. Motivation I developed this technique for a… Read More »

VRF Lite basics

Sometimes while you do routing, you want to do it in a destination-based way and also differentiate routing for different sub-autonomous systems in your AS. Well, such behavior can be enforced by PBR, but it is not that scalable and it lacks some of the nicer things dynamic routing protocols bring to the table. Enter Virtual Routing and… Read More »

Dual-homing with Policy-Based Routing – a case study

Policy-based routing allows network administrator to stir traffic in directions different from the one chosen by destination-based routing and its routing protocols. This can be useful in several scenarios, namely in dual-homing to different ISPs, as well as other special cases. Using policy-based routing for dual-homing General notes on dual-homing The term Dual-homing in its most general meaning… Read More »

Policy-based routing for IP networks

Policy-based routing for IP networks in Cisco routers is a very powerful and precise tool which allows a network administrator to achieve a great many things.  In my opinion it should be considered just as fundamental, as general routing mechanisms. How  it is different from general destination-based routing and what we can to with it is the subject… Read More »