bridge and ping timeout

Hi. I have a Xeon 3.4 with 1 gb of ram. This PC have 4 nic´s (RB44) on an interface bridge. I have a pppoe-server on the bridge interface, when i ping to the IP of the bridge i get 1 to 10 ms of reply but when the traffic is high (about 6000 pck/s and 20 mbs/s) i get ping timeout but the reply is 1-10ms. I have QOS but when i disable this it happens the same.
I tried with stp and rstp and it happened the same thing. The routeros is v2.9.29
Some advice??

M.

Replace the bridge with a switch. Sorry, but there’s no way a software bridge can keep up with an ASIC based switch.

Regards

Andrew