VyOS 1.4 still leverages PPPd internals on the CLI.

pppd supports three options for a default route, none, auto, force.

• none: No default route is installed on interface up
• auto: Default route is only installed if there is yet no default route
• force: overwrite any default route

There are several drawbacks in this design for VyOS and the users.
If auto is specified, this only counted for static default routes - but what about dynamic ones? Same for force, only a static default route got replaced but dynamic ones did not got taken into account.

The CLI is changed and we now re-use already existing nodes from the DHCP interface configuration

• no-default-route: On link up no default route is installed, same as the previous default-route none
• default-route-distance: We can now specify the distance of this route for the routing table on the system. This defaults to 210 as we have for DHCP interfaces.

All this will be migrated using a CLI migration script.