update: sorry false positive - FritzBox7320 has different network controllers.
Theese are 2 Lantiq PEF7071V V1.3 NICs 1Gibt ports (LAN1 and LAN2).
LAN1 is working, LAN2 does not work.
FritzBox7330SL has mentioned:
LAN1 > Atheros AR8035 > 1Gbit port > working
LAN2 > Atheros AR8030-A, SK4P7.4D 1242 CN 10/100 Mbps port > not working
no progress so far 