This option is equivalent to replication being always available. If Ignore schedules is selected, replication occurs at the designated intervals but it ignores any scheduled days and hours. Site links that use the Simple Mail Transfer Protocol (SMTP) transport always ignore site link schedules.
Bridge all site links
Specifies whether replication can occur transitively between sites that are not connected directly by a site link. This option is enabled by default. Domain controllers in different sites can replicate transitively if the following conditions are true:
If you disable this option, you may have to create site link bridges to make it possible for certain domain controllers to communicate.