Bug OR "Feature" - unable to change port address to different subnet with Cisco Configuration Professional Express 3.2.5 on 4321

[IT at Very Very Small Business]

I want to change GigabitEthernet 0/0/1 to 192.168.1.254 from 192.168.2.254 on the 4321 router with Configuration Professional Express 3.2.5 - it clears out the address when I try, but will accept the .2.254 when I put it back.

So bug, or feature? 

[IT at Very Very Small Business]

So I tried the command line way with the following two commands in the appropriate area, aka (config):

interface gigabitethernet 0/0/1
ip address 192.168.1.254 255.255.255.0

And I got the following error message: % 192.168.1.0 overlaps with GigabitEthernet0/0/0

Thing is, GigabitEthernet0/0/0 is set to 192.168.1.253

As is shown in the "show running configuration" snippet below:

interface GigabitEthernet0/0/0
 ip address 192.168.1.253 255.255.255.0
 negotiation auto
!
interface GigabitEthernet0/0/1
 description PrimaryWANDesc_
 ip address 192.168.2.254 255.255.255.0
 negotiation auto
!

I have been playing with 192.168.1.0 - BUT that is supposed to be some DHCP thingy that I'm also trying to figure out here: https://supportforums.cisco.com/t5/lan-switching-and-routing/setting-up-dhcp-on-4321-router-question/m-p/3397503

Below is the relevant snippet from the running configuration:

!
no ip dhcp conflict logging
!
ip dhcp pool Carlton
network 192.168.1.0 255.255.255.0
!

[Diana Karolina Rojas]

Hello,

Every router interface or subinterface represent a broadcast domain, and by nature each broadcast domain has to be unique in the network because routers do its routing decitions based on it, so you can not have 2 interfaces in the same subnet, the only way to do something like that is removing the ip address configuration from both interfaces and configure a BVI interface (a Broadcast Virtual interface) and assing the interfaces to that bridge domain.

Please do not forget to rate useful post.

Best Regards,