Aprilcoco wrote Does your old router have the same issue? Or it worked properly in the same situation? No this issue in old router, old router separate WAN and LAN port.

Does the issue still exist if you power off modem and restart it without connecting switch? ANS: No this issue, only connect modem is correctly, deco m5 have loop prevention or not? When the issue...

Model : Hardware Version : Firmware Version : ISP : Hi All: My network structure have MOD (is a network TV service from my ISP) require, so i use tp-link 105E switch to devide VLAN for this...