In first sorry for the wrong model I declared in this tread but the right my model TL-MR600 is NOT present into different models menu provided ( .. too much new model ? ) 

I am using an ARCHER MR600 just purchased a few days ago, new, and well configurated on all points of innternal as required.

SIM Card is from ILIAD as operator, but the problem remains also trying with different operators SIMs as Vodafone, TIM Italy and WIND-3Italy...

Problem is:

a) the no-ip.com services is set, declared and seem well connected after few seconds of wait (= "connected") with regular flag shown...

b) a first device configurated as "virtual server" is not reachable from external Internet access (!): in detail is an IPCAM with a regular use previously, well accessed within a different my modem, not 3G/4G, on my LAN and proper Ethernet access, always reachable since many years with another similar no-ip.com addressing method.

c) trying ping to specific "user declared" no-ip.com external address, NO RESPONSE is obtained 

d) tryng the same action of "ping" but trying in "direct mode", pointing to the xxx.xxx.xxx.xxx dynamic address shown as assigned by telco operator on appropriate window menu of ARCHER MR660 menu, same NO RESPONSE is obtained 
 
I see other users'post on this forum with different ARCHER 3G/4G model modems but having similar troubles...

Someone has same my difficult with ARCHER MR600 ?   Solved? and in wich way ?

Thanks to all in advance
Sergio