Starbase 211
From Star Trek: Theurgy Wiki
Starbase-211 was a Federation starbase administered by Starfleet. The base was located along the Federation-Cardassian border and consisted of a Sigma-class space station in free space. During the Dominion War it served as a staging area for a number of allied offensive measures that incurred into Cadassian territory.
Starbase-211 is listed as an official posting for Andrew Fisher, during 2381, and is where he was last seen prior to disappearing in an effort to join the crew of the USS Theurgy.