[multiple NIC issue] two NICs in the same subnet problem.

[myronn at seed.net.tw]

Hi, 
    I found an issue for a long time.
    For test requirement without any switch/hub:
    One host has two NICs and with the same subnet setting.
    (local)NIC1: 10.0.0.1/8
    (local)NIC2: 10.0.0.2/8
    (direct connect peer) 10.0.0.10/8
    (direct connect peer) 10.0.0.20/8
    ping command: #ping 10.0.0.10 -c 5 -S 10.0.0.1

    In Linux, while I assign source interface and IP address,
    ex. ping 10.0.0.10 -I eth0  ......packet will be sent by NIC1
        ping 10.0.0.20 -I eth1  ......packet will be sent by NIC2

    In BSD, while I assign source interface/IP address, packet always
    be sent by NIC1.  The NIC2 looks like dead.  Until I set 
    "#ifconfig eth0 down" and NIC2 would be got up. 
    So the ping command parameter "-S" would be broke down in this case.  

    The packets format maybe is correct but NIC2 couldn't work.
    If this is NOT a BUG, please tell me BSD is followed which standard?
    Or what the purpose of BSD to define this behavior?

Thanks & Regards
Myron