Strange Realtek NIC problem.

I bough a new NIC (4 Port RTL 8111G PCI-E) for my home ESXi machine. It's a Dell OptiPlex 3010 i5 @3.2 GHz.

I used a customized ESXi 6.5 image with the Realtek drivers included and everything worked flawlessly with the onboard RTL NIC.

So I thought, an additional NIC with Realtek 8111G chipset wouldn't be an issue. ESXi recognized the card and all the fout ports after boot. Plugged in an ethernet cable to a switch. Link went up. 1000MBit up/down. Perfect I thought.

No. There's no TCP/IP possible on any of the 4 new ports. Link layer seems to work since ESXi displays the link state correctly on every port.

This is the PCI-Info for the new card:

* 0000:01:00.0 Bridge: Pericom Semiconductor PI7C9X2G608GP PCIe2 6-Port/8-Lane Packet Switch * 0000:02:01.0 Bridge: Pericom Semiconductor PI7C9X2G608GP PCIe2 6-Port/8-Lane Packet Switch * 0000:02:02.0 Bridge: Pericom Semiconductor PI7C9X2G608GP PCIe2 6-Port/8-Lane Packet Switch * 0000:02:03.0 Bridge: Pericom Semiconductor PI7C9X2G608GP PCIe2 6-Port/8-Lane Packet Switch * 0000:02:04.0 Bridge: Pericom Semiconductor PI7C9X2G608GP PCIe2 6-Port/8-Lane Packet Switch * 0000:03:00.0 Network controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [vmnic0] * 0000:04:00.0 Network controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [vmnic1] * 0000:05:00.0 Network controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [vmnic2] * 0000:06:00.0 Network controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [vmnic3]

Anybody got an idea what the problem could be here?