LAN + Opt1 bridge or not

[avr]

Hi, thanks for pfSense.

I have normal WAN, LAN and created a new D1 interface for downloads on an Intel i350 (4 net interfaces, gigabit, good cables). I created the rules on LAN to access a server on D1, and it worked, I could RSync, SSH, SFTP, SCP, etc. In general large files should have a larger continued throughput, but in my case the speed came up and down: from 10MB/s to about 200KB/s like a sine wave... very odd. After searching for all kind of solutions, I found an article about creating a bridge between LAN and D1. Did that and it worked (AFAIK): RSync speed from 25 to 30 MB/s sustained. Well good enough, but I'd like to understand what was really happening and why a bridge was necessary... can you please help me or nudge me on the right direction?

cheers