After creating a VPC ECS instance, you can change the private IP address and also can change the VSwitch of the ECS instance.
Log on to the ECS console.
On the left-side navigation pane, click Instances.
Click a region and then click the ID of the target ECS instance.
On the Instance Details page, click Stop on the upper-right corner.
In the Configuration Information panel, click More > Modify Private IP Address.
In Modify Private IP Address dialog, modify the private IP by either of the following ways, and then click Modify.
VSwitch: Select a new VSwitch for the ECS instance from the list.
Ensure the zone of the selected VSwitch and the current VSwitch is the same.
Private IP Address: Enter the new IP address if you do not want to change the VSwitch of the ECS instance.
Restart the ECS instance.