I've noticed the following phenomenon. When a static 1:1 NAT is configured on a MikroTik router (source and destination NAT), after I start a traceroute to the Global IP address that is being translated to a private Local IP address, I always see the last hop being doubled! it seems like the router responds once with the Global IP address, and than once again on the behalf of the internal private IP address.
It's noticeable though that when no NAT is present, the router responds first with it's own IP address on the interface where the traffic was received and than, the last hop replies.
The question is... is this expected behavior?