It sounds like ESXI 7 does install inside the Virtualbox guest, but does not recognize any of the virtual network adapters provided by Virtualbox. (Unless the installer crashes out because the adapters aren't recognized?)
The same thing happens on real PCs all the time. The OS doesn't have drivers for the hardware, so the user must provide the drivers.
I did the same thing for XP in Virtualbox for a while, when I wanted to use the Intel MT Desktop adapter in the XP guest, but XP didn't have drivers for it. I downloaded drivers from Intel, ran them in the XP guest, then XP recognized the MT adapter. Then I found out that the T Server adapter had native drivers in XP.... And then I found out that it didn't matter, Virtualbox pumps the network data into the guest as fast as the hardware can take it, whether the virtual adapter is called 10mbps, 100, or gigabit. They all act as gigabit if the host's adapter is gigabit, etc....
The way I see it, you would have three choices:
1. Get drivers compatible with ESXI for one of the adapters Virtualbox provides.
2. Use a USB-to-Ethernet adapter in the guest to put a compatible adapter into ESXI.
3. Don't run ESXI in a Virtualbox guest.
The possible 4th choice:
IT_TECH wrote:They are going to have to supply different network adapters.. so that esxi 7 can install.
depends on who "they" are. If "they" means Virtualbox, don't hold your breath. The devs will provide network adapters natively compatible with ESXI when paying Oracle customers want to run ESXI in a Virtualbox guest. No other way to say that. Money makes the world go round... (and paying customers have direct access to the devs as part of their support contract so they wouldn't be posting in the free forums).
However, "they" can be users. If you want to model an ESXI-compatible adapter and present it to the devs, they would look at it when they get a chance and if the model is good they might accept it. User-contributed code is implemented at times.