FTP transfer times painfully high, interactive login response time way too long, getting 1 mbps out of your 100 mbps network. While I always prefer to blame the network I have to admit that sometimes it is not the network.
First a little background, TCP has a concept called maximum segment size (MSS). This is the largest segment (of data) that the TCP stack will accept.
Having two interfaces in a module on the same subnet does not give you two interfaces into and out of the module.