System 7.5.2 was the first version with OpenTransport built-in, but OpenTransport wasn't really ready. As a consequence, DHCP did not work correctly and OT even managed to misinterpret the MAC address when reading it from ROM. I recall that Apple's engineers in the OT and AppleShare teams were very helpful at the time, but that still left a lot of problems for us all to pick up.

Note that whilst the Pippin OS is based on System 7.5.2 (required for PCI support), it uses a version of classic networking.