I have a few devices plugged into a Linksys SE2500 switch, which then plugged into an Airport Express (acting as a wireless bridge), which connects wirelessly to some Comcast modem/router. The wireless connection is not the strongest, but I need the devices plugged into the switch to always communicate with each other, without traffic needing to cross the wireless bridge. It seems this is not the case now. Would a "smart" or layer 3 switch help in this situation? I need the switch to be smart enough to keep the high bandwidth data between these devices on the wired side. What do I need to make this happen, ideally without creating a Double-NAT? I am at your mercy!
No need to do anything Tom. Switches are clever enough nowadays to forward traffic out of the correct Ethernet port. In your case, if one of your wired devices wants to speak to another wired device then the switch will forward the traffic intelligently from first device's connected port to the second device's connected port. The traffic wouldn't get forwarded to your wireless bridge.
This was different in the old days when we had hubs instead of bridges. Then, when hubs received traffic on one port, they would forward the traffic out of all ports which obviously was a problem. If you had a hub in this instance then your concern would be valid. Since you don't then no need to worry.
Hope that helps Tom.