Honestly, with 10 servers, a pxe setup is probably overkill. If you're getting used servers (and maybe even if not), you might need to poke them with a KVM to set the boot options so that PXE is an option, and you might want to configure the BMC/IPMI from the console too, and then configure anything for serial over IPMI / bios console on serial ports... do that in your office, since your colo is across the street, and then you may as well do the install too. Then when you install, it should just work and crash cart if not. But, PXE is fun, so...

For PXE / iPXE, there's several stages of boot. You have your NIC's option rom, which might be, but probably is not iPXE. That will hit DHCP to get its own IP and also request info about where to pull boot files. You'll need to give it a tftp server IP and a filename. DHCPD config below

I server iPXE executables to non-iPXE. When iPXE starts up, it again asks DHCP, but now you can give it an http boot script. The simplest thing is to have something like

   kernel installer_kernel
   initrd installer_initrd
   boot

You can also boot isos, but that's a lot easier if you're in BIOS boot rather than UEFI. Better to practice booting kernels and initrds (unless you need to boot things like firmware update isos)

Then you'll have your installer (or whatever) booted, and you might have an unattended install setup for that, or you can just setup a rescue image that does dhcp (again!) and opens sshd so you can shell in and do whatever. Up to you.

the pxe part of my isc dhcpd config is:

   next-server 203.0.113.11;

   if exists user-class and option user-class = "iPXE" {
       option ipxe.no-pxedhcp 1;
       filename "http://203.0.113.11/tftpboot/menu.ipxe";
   } else {
       if option client-arch = 00:06 {
           filename "ipxe.efi-i386";
       } else if option client-arch = 00:07 {
           filename "ipxe.efi-x86_64";
       } else {
           filename "undionly.kpxe";
       }
   }

(This is mostly consoldidating bits and pieces from here [1] )

And I have those three files in the root of my tftp server. There's all sorts of other stuff you could do, but this should get you started. You don't really need iPXE either, but it's a lot more flexible if you need anything more, and it can load from http which is gobs faster if you have large payloads.

If you really wanted to be highly automated, your image could be fully automated, pull in config from some system and reconfigure the BMC while it was there. But there's no need for that unless you've got tons of servers. Might be something to consider if you mass replace your disk shelves with 4U disk servers, although it might not save a ton of time. If you're super fancy, your colo network would have different vlans and one of them would be the pxe setup vlan --- new servers/servers needed reimaging could be put into the pxe vlan and the setup script could move them into the prod vlan when they're done. That's fun work, but not really needed, IMHO. Semi-automated setup scales a lot farther than people realize, couple hundred servers at least. autopw [2] can help a lot!

[1] https://ipxe.org/howto/dhcpd

[2] https://github.com/jschauma/sshscan/blob/master/src/autopw