As of the fixes made in T2502, any manual default-routes configured on a PPPoE interface will be deleted when the interface is torn down, even if they weren't added by setting 'interface pppoe pppoeX default-route' to 'auto' or 'force'.
ip-up.script.tmpl skips the addition of a default-route on interface up where 'interface pppoe pppoeX default-route' is set to 'none' and ip-down.script.tmpl should do the same.
There's at least a couple of good reasons why a manually configured default-route may be required (I'm sure there's more, but these are my situation):
- A default-route has been installed by another dynamic interface (For example via DHCP, or even another PPPoE interface); this route existing will result in no default-route being installed for the new PPPoE interface (For the default-route setting of 'auto') or it will replace all existing default-routes (For the default-route setting of 'force')
- A administrative distance other than 1 is required for this default-route, so this has been installed as a manual default-route and the 'default-route' setting explicitly set to 'none'
As it stands, things somewhat behave as expected on PPPoE interface up however when the PPPoE interface goes down the router can be left with no default-routes at all.
Ideally, if 'default-route' is set to 'none' any default-routes associated with this PPPoE interface should be ignored.