Brownfield migration from PROFIBUS DP to PROFINET typically relies on "proxies" (Siemens IE/PB Link, Hilscher netTAP, ABB gateways) that expose a whole PROFIBUS segment as a single PROFINET device seen by the modern PLC.

A proxy such as the Siemens IE/PB Link sits on both networks at once. On the PROFINET side it appears as an IO Device with its own GSDML and is configured normally in TIA Portal. On the PROFIBUS side it plays the role of DPM1, owning and parameterising the existing DP slaves. The proxy then translates cyclic data and diagnostic information transparently between the two worlds. This makes it possible to replace the original PROFIBUS PLC with a modern PROFINET CPU without touching the field wiring or the installed DP slaves, which is precisely the gradual five-to-ten-year migration story PI promotes.

Size the proxy carefully: the cyclic budget of the PROFINET side and the original PROFIBUS T_TR both apply, so the proxy can become the bottleneck if you stuff too many slaves behind it.