wan 1 with lan bypass

hello support

first i have a static public ip in wan1 after config enable the drop-in mode settings (WAN 1 with LAN bypass) the WAN ip and LAN ip are same just curious here and then i received call from the ISP why my 2 mac address are the same IP. is this really normal for drop-in mode? or just leave the wan1 dhcp and assigned LAn bypass as static?