AB BOOTP issues

I am having some trouble assigning an IP address to a Compact Logix 1769 controller. When I first got the PLC I used BOOTP to assign the IP address of 192.168.0.2 with a network switch address of 192.168.0.8. Note I did not use Disable BOOTP. Now I needed to change the network switch address to 192.168.1.8. After changing the the switch address, I powered off the controller and powered it back on. From my understanding, the PLC does not have an address assigned at this point. However, when I tried to use BOOTP I could not assign an address to the PLC. I could communicate with other devices on the network but just got a timeout when trying to communicate with the PLC.

After reading up a little on this I am still not sure what my issue is. I have also tried changing the network switch address back to the original address of 192.168.0.8. After cycling power, I verified the PLC did not have an IP address assigned and was successfully able to assign the old address back.

From what I call this is not a firewall issue because when I disabled it I got the same results. Also, I made sure to change the IP on the computer I was testing this stuff on and verified that I was connected to the network.

Any thoughts as to what I am doing wrong here? It seems like I cannot assign an address unless the network has the 192.168.0.xx format.

Is it a managed switch? Maybe it is v-lan'd for PLCs on certain IPs. That's how my plant is

I'm guessing you meant to say Gateway address so you'll need to change your PLC address first including the gateway address.

It is a managed switch but I did not put any restrictions on certain IPs and I am pretty confident no one else has touched anything.

Instead of the long specifics of my problem I am going to try posting my general understanding of what I am trying to do and see someone show me where I am going wrong.

I have a CompactLogix 1769 that had IP address but was powered off and Disable BOOTP was not used. Once I power it on, it no longer has an IP address and I need to use BOOTP or some other method to assign the IP address. When I connect it to a network switch I can assign it an IP address but the first three sets of numbers must be the same, ie if the network switch address is 192.168.1.8, I can only assign it an address starting with 192.168.1.xxx. My issue is if the network switch has a format of 192.168.0.xxx I can assign the PLC an address of the format 192.168.0.xxx. If the network switch has a format of 192.168.1.xxx I should be able to assign the PLC an address of the format 192.168.1.xxx. but cannot and have no idea why.