Hi
AFAIK the span port blocks all outgoing traffic on 3750´s.
I am sorry but I must ask.
Why would you want that ?
I love the fact that i do not have to worry about disturbing the server on the other end when sniffing by answering a packet or something.
and no need to make filters for capture that i do not accidental gets a lot of traffic that is control traffic (ie to my own pc).
My advice would be that If you need control traffic, set up another interface on the sniffer computer and use that for control traffic.
The only time this have been a problem was when I forgot about a monitor session configuration i had made and a month later accidentally connected a pc to that port.
I could get no connection, no dhcp address and so on then i connected my laptop and was quite confused since i did se traffic, after a little while i realised that i saw traffic not destined for this computer and checked the configuration and sure enough it was a destination port.
Ever since then i try to plug each port i use as a monitor destination port with a RJ45 plug that is blind (without cable). That way i know where my destination ports are and no mistakes can be made.
Good luck
HTH
