Hello,
we have this problem with increasing latency on ETH interface of routerboard. After RB boot, latency on device is <1ms. After few days is latency increase and after RB reboot is back <1ms.
See this graphs:
RB921UAGS.jpg
We have this configuration:
On ETH1 port are 2 VLANS, one VLAN is for management, second VLAN is for data. Data VLAN is bridged with WLAN1 interface.
This configuration we have on RB433AH and problem with latency isnt.
RB433AH.jpg
In this situation, we must reboot RB every second day.