freebsd stable - Oct 2011 - Using serveral bridges with only one span port

Hi all,

  Is it possible to configure three bridges on a FreeBSD 9 host and 
redirect traffic from these three bridges to only one span port?? I am 
thinking to configure something like this:

cloned_interfaces="bridge0 bridge1 bridge2"
ifconfig_bridge0="addm fxp0 addm fxp1 span em0 up"
ifconfig_bridge1="addm fxp2 addm fxp3 span em0 up"
ifconfig_bridge2="addm fxp4 addm fxp5 span em0 up"

  .. or do I need to configure one different physical interface as a 
span port for every bridge?? Like this:

cloned_interfaces="bridge0 bridge1 bridge2"
ifconfig_bridge0="addm fxp0 addm fxp1 span em0 up"
ifconfig_bridge1="addm fxp2 addm fxp3 span em1 up"
ifconfig_bridge2="addm fxp4 addm fxp5 span em2 up"

Thanks.

-- 
CL Martinez
carlopmart {at} gmail {d0t} com