I bought two RB493G. One was installed in a POP few months ago.
Today I installed the 2nd one on another POP (both are connected to the backbone too).
I started to see on log of one of the routers the interface loop detection alarm (mac address duplicate)
While figuring where was the problem I realized both RB493 have the same MAC address for ether1..ether9. And casualty, both ether2 was connected to the backbone there was a MAC address conflict (as both MACs have different IPs)
Finally I changed the connection of one router to another ether port in order to have different MACs on the same LAN.
How is this possible? Any manufacturing issue?