The ISP is handing the gateway as a private IP and that's common for a PPPoE link and not normally an issue. I have that here. But, yeah, using a 192.168.x.x address is far more likely to conflict.
However, exactly as I also see, that gateway does not respond to ping. You should set the monitor IP to something further upstream like 8.8.8.8 so you get real monitoring data for the link.
Steve