There are many similar routers in my network that have 10.100.NN.1 ip addresses:
10.100.1.1, 10.100.2.1, etc
Autodiscovery is not have possibility to add all 10.100.NN.1 addresses to discovery rule at that moment.
Another example: https://www.zabbix.com/forum/showthread.php?t=6791
I belive, cisco wildcard mask will be good solution for that.