You configured an interface with an IP address and committed the change. You then committed a change that added an exception in a firewall filter to allow this network through the filter. You…

The Junos OS configuration stores previous committed configurations, indexed starting from 0 (the current active configuration). `rollback 1` would revert to the configuration before the most recent commit, and `rollback 2` would revert to the configuration before the second-to-last commit, effectively undoing the last two changes.

`rollback 1` would undo only the most recent commit (the firewall filter change), not both the interface and firewall filter changes.

`rollback 0` rolls back to the current active configuration, which makes no changes.

`rollback 3` would revert to the configuration state three commits ago, which is more than necessary to undo the last two changes.