BOOTP - Bootstrap Protocol
Yes, the guy who put in the address originally told me that he could have forgotten to disable bootp.
However, I used a Micrologix1100 often back when I was in school. It always retained its ip address through power cycles. I don't think I ever disabled its bootp because in the Rockwell Bootp program, I always saw it sending bootp requests with its MAC and last IP address.
So, why does Powerflex lose its IP address at power cycles when MLX1100 keeps its ip address? Is that by design?
The AB DHCP/BOOTP Utility is not just an interface to assign IP addresses. It acts as an IP address configuration Server.
When you open the utility and receive a request from a device, this is a Client requesting an IP address from a Server. When you assign an address in the utility, you are configuring the Server to establish a relationship with the Client. So the Server will then always recognize the Client i.e. its MAC address, and assign the same IP address automatically.
So the Powerflex and the MicroLogix are Clients of the BOOTP Server. Normally when we assign Clients an initial IP address, the intention is to assign a Static IP address. So we use the utility to disable BOOTP while assigning the address. This prevents the device from clearing it's IP address and sending BOOTP UDP requests upon a power cycle.
If your colleague left BOOTP enabled in the PowerFlex while assigning an IP address, then upon a power cycle, it cleared its IP address and began sending BOOTP requests. If a Server is not there to service these requests, then the Client i.e. the PowerFlex, will never be assigned an IP address.
When you had a computer connected to a MicroLogix 1100 in school, you created a relationship between the BOOTP Server on the computer and the MicroLogix Client. With BOOTP always enabled in the MicroLogix, and the Server running on the connected computer, the MicroLogix could clear its IP address upon a power cycle and request a new IP address from the Server. As you had a relationship already established, the Server would re-assign the same IP address to the Client once again.
I always saw it sending bootp requests with its MAC and last IP address
You will not receive BOOTP requests from a Client that already has an IP address.
When you looked at the requests list, after powering up, you were seeing the MicroLogix MAC address with its automatically assigned IP address from the Server.
If you did not have the Server utility running, or the computer connected, then, upon a power cycle, the MicroLogix would have cleared its IP address and not have had its BOOTP requests serviced.
The tradesman that understands his tools, understands his craft.
G.