Your hardware has to support it.
HP servers have something called an ILO,
IBM/Lenovo servers have something called an IMM.
These require dedicated network ports. (They don't use your normal LAN port).
You assign these an IP address. (usually in the UEFI somewhere) and usually
If you're working on a "real" IBM powerPC series. It uses something called the MMC.
You should have a local console attached (with a keyboard). It will always be at the
MMC interface by default.
On Dell/HP/Lenovo x86-64 systems. The ILO/IMM address will be somewhere in the
UEFI/BIOS. Generally under "ILO settings". Usually there is a section for network under this.
If you already have Linux installed on the server. You can install something called
ipmitool (most major server distro's have this in their repo somewhere).
You can access "some" of the ilo/imm settings through the ipmitool.
This is not for the uninitiated. This is not a beginners tool.
I know saying read the man pages sounds like a cop out.
But in my opinion, this is one tool that if you can't understand the man pages,
you probably shouldn't be using it.