The Federation-Tzenkethi border was a shared border between the United Federation of Planets and the Tzenkethi Coalition.
The Helaspont Nebula was located not far from the border. (DS9: "Adversary")
During the Federation-Tzenkethi War most of the fighting was contained to the regions around their shared border. (The Dominion War Sourcebook: The Fires of Armageddon)
External link[]
- Federation-Tzenkethi border article at Memory Alpha, the canon Star Trek wiki.