when i build nether portal on multiplayer .

when i build nether portal on multiplayer and then go back to the overworld and build another portal

What I expected to happen was...:
a new portal will be create either in the overworld and nether.

What actually happened was...:
it just bring you back to the old portal , the first portal that built

1.build nether portal on multiplayer
2.then go back to the overworld
3.build another portal