BGP Default-Originate insights

BGP has multiple ways of advertising a default route to its neighbors;  the neighbor default-originate command is one of these methods and used to advertise a default route to a specific neighbor. Below are some characteristics of the default route advertised by this way.

Originator router:

• Default route does not need to be existing in the routing or BGP table before advertising.
• The default route will not be installed in the BGP table as local.
• The default does not appear in the output of the command show of the advertised routes.
• The route can not be filtered outbound by the originator.
• The default route can be sent to both IBGP and EBGP neighbors.
• The advertisement can be conditional using the route-map keyword.

Receiver router:

• The default route is installed in the BGP table with the originator's IP as the next hop.
• The default route can be filtered inbound.
• Normal route is advertisement rules apply to the route in the BGP table.
• Normal route reflection rules apply to the default route.

If you have more information, ideas or best practices of using this command please share it with us in the comments section.