IOS 15 great SW but without Data or UC license on it - no IP SLA. Without that you have no easy way of configuring floating static routes with tracking and doing IP reachability tests of your default GW.
This solution is doing pretty much the same but without IP SLA at all - we are going to utilize only the EEM with track feature like before. So basically, EEM script would be something like this:
event manager applet chilly
event timer watchdog time 10
action 1.0 cli command "enable"
action 1.1 cli command "ping [DF-GTW-HERE] repeat 3 timeout 2"
action 1.3 regexp "!" "$_cli_result" result
action 1.4 if $result eq "!"
action 1.5 track set 100 state up
action 1.6 else
action 1.7 track set 100 state down
action 1.8 end
Before putting this EEM script live configure adequate track object, like this:
track 100 stub-object
Off course if you need you can fine tune this EEM script...for example set timer to 5 sec or similar.
Now you can configure your floating static routes like before...with higher and lower AD on them...