Block replication from test DC to Production DC

Hi Experts

Our client needed a test DC with all production data in, so we promoted a server to test DC and connected to the network and allowed to replicate

Test DC is ready with production data, Now we cannot afford to have it in the network as the client makes any changes to expirement in the test DC, it will replicate to production.

I need to know how to proceed further

1) Disable the outbound replication from TEST DC and leave it in the network

or

2) Isolate it from the network.

NOTE: Cleints will comeback again to update this test DC , after certain period of time approx 1month

Please let us know only if you sure as it will impact the business