One of those readers that prefer to remain anonymous has left an interesting comment to my post “Almost-dynamic routing over ADSL interfaces”:
You do not need the route "ip route 0.0.0.0 0.0.0.0 Dialer0 10 track 100" and the tracking if you configure "ppp ipcp route default" on the dialer interface. Works the same way... :-)You might be wondering why Cisco's engineers decided to pollute IOS with yet another feature. The problem they had was the way PPP over Frame Relay is implemented: it uses virtual interfaces and although you have a very static connection, you cannot bind a static interface name to it. A dynamic interface (with potentially changing name) is cloned from the virtual template every time the PPP-over-Frame-relay session is started. Obviously you cannot configure a static default route pointing to it in advance, so you need yet another feature to do it (I'll not even try to figure out how to create non-default static routes pointing to cloned interface).