We have two ACS servers. Our goal is to make one ACS to setup as primary and the second one as standby on the routers & switches, so when the primary is down, we can login the equipment via the secondary ACS without any issues. But it seems it doesn't work properly. If the primary ACS is down or disconnected, we are not able to login the switch Here is part of configuration on the router.

tacacs-server host 192.168.100.1 key cisco

tacacs-server host 192.168.100.2 key cisco

Please help.

Thank you.