While that traffic is annoying, I sincerely doubt that it's causing any detectable latency, at least not at the levels that you posted. STP traffic is legitimately broadcast every two seconds; you could adjust the interval if you really wanted to (or disable if it's an edge port), but a packet every two seconds is trivial. Try to track down the source MACs of those 192.168.1.1 ARPs; you'll need to google the vendor prefix(es) for GigaByte to get the full MAC (e.g. 12:34:56:E5:7B:FE), then check your switches for which port they're known on. It's possible that you're seeing traffic from that 192 network being inadvertently bridged onto your 10.34.0.0.