T-Mobile Cellspot - UDP Port 123 Blocked

[GuidoD]

Hello all,

I'm an otherwise happy Fios customer.  However, port 123 UDP is blocked and no incoming connections allowed on port 123 UDP. It's not my modem/firewall settings blocking it -- it's Fios filtering this

I've done many things to double, triple, quadruple check that it's not my router blocking it. I have worked on two different occasions with "Router Configuration Specialists" for a total of 3.5 hours . swapped routers. swapped cellspot. Everything seems to work except Port 123 UDP . The other two ports required (500 & 4500) work fine. Just 123 UDP is blocked

My problem is that it's really difficult to describe this situation with phone tech ( I have tried about 20 times) because they are confused about the problem. They walk me through reconfiguring the router setting specific rules a number of different ways and even placing the device into DMZ..... the traffic is somehow being dropped on the network, not my house. I've tried several times. 

Does anyone know how I can go about getting UDP 123 unblocked? Is there someone at Fios who I can reach out to that might understand the situation?

[Cang_Household]

What service is trying to use UDP 123?

UDP 123 is reserved for Network Time Protocol (NTP) as per IEEE's recommendation. This port is reserved for synchronizing time with atomic clocks around the globe.

[Capricorn1 · Accepted solution]

I can't say for certain since I'm not using a Verizon router for my Fios internet, but Windows Time Service uses UDP port 123. Are you having issues with Windows machines (re-)setting their time? If you go into the Date & time desktop app, can you click on the Sync now button and see the date of the last synchronization change? If so, I'm pretty sure you are getting data through UDP port 123.