Consequence of changing SUBNET-mask on running PLC
The change(s) will take effect at next Controller Reset (short push of the reset button or 24V power cycle).
Your version may be affected by a software problem arising from using RNRP explicit adressing mode and certain settings. Be sure to download and read the Product Alerts published on the matter at ABB Library (ABB Intranet access or a subscription for external access is required).
If the controller should use RNRP for automated routing and network supervision, the implicit addressing mode requires a /22 subnetwork mask. For example, if the PLC is currently set with 172.16.80.151/22, RNRP will self-configure (Area 20, Node 151). If you change to a /24 subnetwork mask and would like to keep RNRP running "as is", you must provide explicit parameters, e.g. Area 20, Node 151, Local Flag 0 and Path 0 on Ethernet 1 settings.
RNRP and available addressing modes are explained in detail in the System 800xA Network Configuration User's Guide.
Running RNRP is not a requirement, but a recommendation.