Serial Port Connectivity
On the R181, use the RJ45 'cisco console' cable. Something like this Link to example product at Amazon.
If you get the one with the DB9 rather than the USB, it *may* need a Null modem cable.
The system will take as much as 10 minutes to boot. This is mostly because of the very verbose memory diagnostics at start up (and before SOL and VGA console output). So, the RS232 serial interface provides more information and will give you an indication that the system is not 'hung' during that time. After you are familiar with this; the RS232 can be used for a console, or 'ssh' should work (provided the service is running and the system is attached and has an accessible IP on your subnet). It can also be set aside should more information is desired.
Lastly, If you put the BMC connector onto a DHCP served network, you can use the BMC WebUI to open a console via its web server (UID/PWD: ADMIN/PASSWORD). If you do use the web console; you will need to enable popups on your browser (disable popup blocking) or all you will get is a warning from the browser.
Serial Port Location:
IPMI and Serial Over LAN
IPMI SOL is also an option once you get the BMC IP address for the 1Gbe management port.
Server Management Port Location: