Original post is at the end.
Welcome to the wonderful world of multi-homed hosts on Sun. All interfaces on the same box will have the same MAC address. Sun refuses to acknowledge that this is a bug. The MAC address is based on the PROM, so by default it will be the same for all interfaces on a machine. You can set a different MAC address to use with ifconfig if you want, but since the interfaces should be on different networks, having duplicate MAC addresses should not be an issue.