About using Cisco SLA to monitor non-direct connection network down to delete routes

It took one night to study some people's claim that "you can use Cisco SLA to monitor a non-direct connection network down to delete a local static/default route", which I personally think is impossible.

Some people's original intention should be to avoid invalid data packets forwarded by the router. Because the non-direct connection network is disconnected, the local router still forwards the data packets according to the original route because the direct connection route is not down, however, after my experiment, it is impossible to achieve the following:

1. sla icmp-echo packets must also be forwarded according to the local route. If the local route is deleted, the SLA will never successfully reach the remote destination, and the track will never meet the conditions, the route cannot be restored.

2. If the target is inaccessible and the track condition is not met, the static/default route of the track will be deleted.

3. The original default/static route still exists in the routing table, and data packets are still forwarded according to this route, which does not prevent the router from forwarding invalid data packets.

4. Even if there are redundant lines, the SLA still cannot achieve the expected effect. Redundant lines are usually the default routes.

If the target of the SLA is an address that can be reached by a redundant line, the track will be continuously down-> up-> down. The reason is understandable. See figure 1;

If the target of the SLA is reachable, the track will never be restored. The reason is as follows: 1

Conclusion: The use of SLA to detect the down and up of a non-direct connection network is not feasible, and it is not necessary to test the direct connection network. In short, the SLA is very useful in this regard. Consider other uses of the SLA.