Some servers allow you to share an Ethernet interface between the host and the management controller (BMC, IPMI, iLO, iDRAC, etc.)
I always found this strange and have been wondering how it works. Today I learned about NC-SI, the network controller sideband interface, and it's even more cursed than expected.
Fortunately the spec is freely available, so let's have a quick look at it: https://www.dmtf.org/sites/default/files/standards/documents/DSP0222_1.1.1.pdf
[thread]
@vidister How strongly does this rely on the host (a) not doing something silly like flooding the interface with outgoing packets (b) not messing up the NICs configuration in some standard way (c) not doing things that are unlikely to happen by accident but if they happen will mess up the BMCs connection?