Question

Network blocking UDP?

M
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I use mosh (https://mosh.org/) to connect to some servers and have for years, which has normally worked fine, but for the last couple of weeks it has not worked over the tmobile network at all, the UDP packets never reach their destination.

I can SSH into the servers fine and run commands over SSH, but when trying to switch to mosh, which uses UDP, all UDP packets to the host are dropped and never received, while if I switch to a wireless network then they are received at the destination fine, and have tested over multiple different ISPs to different destination servers.

Support are useless, as expected when it comes to asking indepth questions about networking protocols.

16 replies

R

Anybody been able to get UDP working yet?

P
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I would like to update this thread with information I received this week in regards to the problem at T-Mobile with UDP blocking. I recently thought I had an issue with drivers on my laptop in regard to my Nextiva Windows phone app. I could connect on calls but neither me nor the person I was calling could hear each other on voice calls. I was connected on my T-Mobile MiFi Inseego M2000 with a 5G connection over WiFi to my LG GRAM laptop. After 1 ½ hours with Nextiva support we tried my Verizon Inseego MiFi 8800L and it worked flawlessly. As a member of RV Mobile Internet Resources, I reached on the forum and it was suggested that it could be a not very well documented issue with T-Mobile blocking UDP on 5G connections. It was suggested that I should try the T-Mobile MiFi Inseego M2000 on a dedicated 4G LTE connection and viola it worked like a charm. On RV Mobile Internet Resources center forum Andy linked this post. So I figured I would post the solution here too, hopefully this help someone and get the attention of T-Mobile to document that there is an issue with UDP blocking on 5G.

 

For my Juicebox issue, I have tried T-Mobile Hotspot off my phone on 5G and then LTE, neither works.  Seems the problem is with the whole T-Mobile network.  I think I will just have to switch to another provider.  Cox is offering StraightUp Internet (via Boost Mobile) for $50/mo.

P
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My wifi thermostats and wifi lights work but my Smart EVSE no longer connects to Juicebox server after switching to T-Mobile.  Below are the list of Ports & Protocols Tech Support sent me.  There are almost nothing I can configure on the 5G Internet Gateway, so not sure if there is a fix/workaround.  I may have to cancel my T-Mobile 5G Internet.

 

 

I have the Sagemcom Fast 5688W Gateway.

https://www.t-mobile.com/content/digx/tmobile/us/en/support/home-internet/sagemcom-gateway.html

 

BTW, seems Tech Support does not want to be contacted online.

 

H
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I have the same issue using I have a module that controls and monitors my home alarms. I have 2 gateways at 2 properties that worked fine for 3 months.. last week both of them are no longer talking to the server from the monitor. Talked to the module company and got

The Envisalink uses UDP port 4021 for
communication so the router is blocking that port, possibly over UDP
only. This may be in effort to block VPN usage or possible Bittorrent
services as both use UDP on non-standard ports.
 
Ran some software to check if the port is open at the server and NOPE… Tmobile needs to get it together or im out…
 
S

Changing the PDP to IPV6V4 didn’t solve the issue for me.  It was already set that way.  I switched the APN from fast.t-mobile.com to B2B.tmobile.com and VPN’s started working.  VPNs that depend on UDP.  The down-side is that the connect (off VPN) seems to be about ½ the speed, so when I’m not using VPN I switch it back.  Hope this helps someone out until T-Mobile can STOP BLOCKING UDP.

 

Sean

T

I've been trying to figure out why my ham radio dmr hotspot isn't working now when I'm mobile. I've reset devices and finally came across this. So annoying and has been absolutely frustrating. TMobile needs to fix this for those of us wanting and needing these voice capabilities. Glad to know I've not lost my mind. But may need to look for a cheap hotspot option that isn't T-Mobile. 

T
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Today I called T-Mobile  Home Internet for the 3rd or 4th time.  The T-Mobile trashcan modem lacks  UPD port settings features.  While they say they are working on the issue they have suggested that I get a router to control the UPD setting.  Does anyone have any recommendations?

D

It seems to me from testing that T-Mobile's 464XLAT implementation has recently been changed to block UDP.  To bypass the problem if you change your phone/hotspot's APN (Access Point Name) to use IPv4/IPv6 instad of just IPv6, then UDP starts working on 5G (and LTE).

Thanks for the update I'll give it a try.

T

It seems to me from testing that T-Mobile's 464XLAT implementation has recently been changed to block UDP.  To bypass the problem if you change your phone/hotspot's APN (Access Point Name) to use IPv4/IPv6 instad of just IPv6, then UDP starts working on 5G (and LTE).

D

I would like to update this thread with information I received this week in regards to the problem at T-Mobile with UDP blocking. I recently thought I had an issue with drivers on my laptop in regard to my Nextiva Windows phone app. I could connect on calls but neither me nor the person I was calling could hear each other on voice calls. I was connected on my T-Mobile MiFi Inseego M2000 with a 5G connection over WiFi to my LG GRAM laptop. After 1 ½ hours with Nextiva support we tried my Verizon Inseego MiFi 8800L and it worked flawlessly. As a member of RV Mobile Internet Resources, I reached on the forum and it was suggested that it could be a not very well documented issue with T-Mobile blocking UDP on 5G connections. It was suggested that I should try the T-Mobile MiFi Inseego M2000 on a dedicated 4G LTE connection and viola it worked like a charm. On RV Mobile Internet Resources center forum Andy linked this post. So I figured I would post the solution here too, hopefully this help someone and get the attention of T-Mobile to document that there is an issue with UDP blocking on 5G.

A
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Still blocked for me, support still useless.

For me, it’s blocked on LTE too.

Does anyone have a way to bypass the script-readers and get to someone on their network team?



Nope; I was supposed to have someone call me back a week ago after talking to the software team. Never called back then I kind of said screw it after that, started to feel like I was working a full-time job just dealing with this; Granted I am about to move soon so I dont really care right now. 

M
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Still blocked for me, support still useless.

For me, it’s blocked on LTE too.

Does anyone have a way to bypass the script-readers and get to someone on their network team?

A
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They are indeed blocking UPD connections on 5G networks

For the unaware; UPD is a network protocol that allows you to send packets of data without waiting on a reply from the host server. It is commonly used in Live or real-time services such as voice communication on discord or online gaming, or other low-latency applications.

Customer service appears to have no knowledge of this which means it is software engineers and higher up management.

It may be to clear up the network for their home internet service which also uses 5G service.

Apparently my last comment got hit by moderation and I do not remember using vulgar language in that one so I dont know.

For me, they blamed inseego for the issue. In any case, the only current fix to using UPD is to lower your network to 4G LTE which sucks, I know. In my case, 5G is 35ms, 4G LTE is 70ms, so it really hurts.

Hopefully they revert the changes to the backend.
Your only other choice is to move to a different company.

A
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They are indeed blocking UPD on 5G connections and lying about it.

For me they tried to blame Inseego.

To fix it, I had to drop down to 4G LTE.

I use discord and play video games over 5G; Voice in discord uses UPD, chat\text uses TCP. Everything that runs through TCP works fine, while everything that uses UPD does not work on 5G.

Anti-consumer basically. Got too big for their own good.

Please note that customer service is only there to follow a script; even they are unaware of what is going on with higher ups. The fact that you even know what UPD is means that you know more than 99% of their customer service.

 

For those of you that do not know; UPD is a network protocol that typically is used for low-latency applications that do not wait for a reply from the connected server. It is most commonly used for voice communications, online gaming in Real-time, pinging, or in Mosh’s case; allows you to send packets without waiting on a packet to return; allowing it to appear latency-free. Compared to traditional where it seems really laggy because it is waiting on a reply from the remote service.

A
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I have the same problem. I'm a ham radio operator and some of my equipment needs to connect to servers using UDP but looks like t-mobile is blocking UDP access to internet.

Trying to talk to customer service about UDP, servers, etc, is like talking to a cow. 

M
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