Is your modem connected via pppoe, or ethernet?If you want to have help you have to post your basic network structure.Also just as a tip, if its pppoe it's not going to work seamlessly. Also the failover with it (in my tests) was prone to wonky behavior. The patching of an opnsense takes like 2-3 minutes, in which the reboot maybe takes 1 minute. Only bigger upgrades every half a year take some more time. So you should think about if the usecase is really there. CARP and HA setups are quite complicated.Here for a basic CARP HA setup: https://docs.opnsense.org/manual/how-tos/carp.html