After read/write splitting is enabled, you can change the read/write splitting address.
Changing the read/write splitting address will interrupt database connections and services. Therefore, change the read/write splitting address during off-peak hours or when services are stopped.
The new IP address is not in use and must be in the same subnet as the RDS for MySQL instance.
You can change the read/write splitting address for DB instances with read/write splitting enabled.
Alternatively, click Database Proxy in the navigation pane on the left. On the displayed page, click Modify next to the Read/Write Splitting Address field.
In-use IP addresses cannot be used as read/write splitting addresses.