Does the TP-Link MR3220/3420 work with Huawei BTU ?

Yes. But u need to use other firmware like ddwrt or openwrt. But can't use VoIP.  Unless u modify the Huawei use port3 to conect the voip

stock firmware. When i hooked up to original thomson router, internet and phone both works. But when i use WDR4300 and extend to thomson, the phone doesn't work. Did i miss any setting in order for the phone to work?