(Optional) The keyword secondary means the IP address is a secondary hot standby router interface. If neither router is designated as a secondary or standby router and no priorities are set, the primary IP addresses are compared and the higher IP address is the active router, with the next highest as the standby router.
As you can see from the above explanation the keyword forces that device to be the standby router for that group. In other words, this command is an alternative to designate one device as the active router and the other one as a secondary/standby router.
Hence, you can't use the second configuration as that would force both devices to be the standby router for 172.16.1.0/24 subnet.
I tried the same setup in my lab, the one command lookup tool shows, and that confirms your suspicion. Yes, the 'standby ip [secondary]' command works in conjunction with secondary address and the router that's active for primary subnet becomes the active router for all the secondary subnets as well.
BTW, all the standby addresses, including the ones with secondary keyword, have to be configured under the same group for this to work. If you decide to choose this configuration, don't forget to configure the 'standby preempt' command on the active router as the example doesn't show it.
Hopefully, this should help you decide whether this is the configuration you need.
We are pleased to announce availability of Beta software for 16.6.3.
16.6.3 will be the second rebuild on the 16.6 release train targeted
towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are
looking for early feedback from customers befor...
Introduction Featured Speakers Luis Espejel is the Telecommunications
Manager of IENova, an Oil & Gas company. Currently he works with Cisco
IOS® and Cisco IOS XE platforms, and NX to some extent. He has also
worked as a Senior Engineer with the Routing P...
In this session you can learn more about Layer 3 multicast and the best
practices to identify possible threats and take security measures. It
provides an overview of basic multicast, the best security practices for
use of this technology, and recommendati...