In this blogtorial we will explore one of the methods by which we can advertise a default route to BGP neighbors. One of my colleagues last week asked "would we loose the BGP default route advertisement if the advertising neighbor lost the default route in its own RIB" and honestly I wasn't sure. And I hate being unsure of "something" network related. So I did what any curious person would do, I lab'd it up and it turns out that default route advertisement is not lost when you loose the default route in the routing table, although you can certainly configure it as such.
Here is a simple topology to get started.