Drivers for NIC (igb vs em)?

[jester at panix.com]

This is (I think) a basic networking hardware question. I'm actually running FreeNAS 11.3, but I assume this relates to the underlying system.

I have a motherboard with two built-in NICs. These appear as em0 and igb0. I'm just wondering why these are created with different drivers, instead of as em0 and em1 or igb0 and igb1. Is this something I have any control over?

(I originally came to this question when I was considering using link aggregation with LACP, and it's recommended to do this only with the same NIC driver. I've subsequently decided not to do this, but remain curious about the underlying driver issue.)

If it's relevant, the output of lspci for the Ethernet controllers only:

$ sudo lspci -v

[...]

00:1f.6 Ethernet controller: Intel Corporation Ethernet Connection (2) I219-LM (rev 31)
        Subsystem: ASRock Incorporation Device 15b7
        Flags: bus master, fast devsel, latency 0, IRQ 16
        Memory at df100000 (32-bit, non-prefetchable)
        Capabilities: [c8] Power Management version 3
        Capabilities: [d0] MSI: Enable+ Count=1/1 Maskable- 64bit+
        Capabilities: [e0] PCI Advanced Features

02:00.0 Ethernet controller: Intel Corporation I210 Gigabit Network Connection (rev 03)
        Subsystem: ASRock Incorporation Device 1533
        Flags: bus master, fast devsel, latency 0, IRQ 19
        Memory at df000000 (32-bit, non-prefetchable)
        I/O ports at e000
        Memory at df080000 (32-bit, non-prefetchable)
        Capabilities: [40] Power Management version 3
        Capabilities: [50] MSI: Enable- Count=1/1 Maskable+ 64bit+
        Capabilities: [70] MSI-X: Enable+ Count=5 Masked-
        Capabilities: [a0] Express Endpoint, MSI 00
        Capabilities: [100] Advanced Error Reporting
        Capabilities: [140] Device Serial Number d0-50-99-ff-ff-c1-f6-ab
        Capabilities: [1a0] Transaction Processing Hints

Thanks.