How to unblock IPs in bulk?
There are several options, choose depending on your requirements:


You can use module Blocked IPs Expire to add an expiration date to IP blocks when adding them. The Drupal cron job will remove the blockings after expiry.
You can remove all of the IP blockings at once with this drush command:

drush sql-query "TRUNCATE TABLE blocked_ips"

You can remove just some IP blockings (e.g. an IP range) with similar drush commands. For example to delete all IPv4 blocks:

drush sql-query "DELETE FROM blocked_ips WHERE ip LIKE '%.%.%.%'"



Note that auto-banning users and IP addresses after a number of unsuccessful login attempts is a different Drupal Core mechanism, resulting in entries in table flood – more details. To remove these bans, the Flood Unblock module can help you. (But that mechanism is out of the scope of this question anyway.)