Tongfamily (Richtong.com Sync)

Long story short hotspotting is great and we had great luck on light speed (T-mobile) on US mobile with Nexus 6 phones but sigh not this time:

1. Us mobile had a great promo. Get dark star unlimited premium and then they give you flex starter for free for a year.
2. The connection to my old iPhone X and xiaomi 13 pro worked great as long as you have a physical sim and you hand set the APN on Android or download it for an iPhone.
3. When you get onto US Mobile or you switch networks (they support three!), you have to change your APN settings. They don’t really explain this when you choose switch or activate. You have to get a new sim physical or eSIM AND change the APN settings. With iOS it’s a download. With android ur typing obscure stuff into settings.
4. iPhone X is on 16.7. And I couldn’t get anything to work. The IP address wasn’t assigned. Turns out on AT&T you have to be on iOS 17. Sigh. So phone and data work but not hotspot. I don’t really get this. But since ip addresses are failing it needs more research.
5. Xiaomi 13 Pro. Even stranger. I got an IP address but no network connectivity. On asking they said, it’s not compatible. Sigh. The APN is exactly as they asked for but an obscure Reddit post says sure ip4 is enabled. But looking at what’s my ip I see an ip4 address and I get an ip4 address from them.
6. Final obscure thing to try is USB tethering. I tried this with Ethernet tethering and same problem. I get an address but not routing.
7. Final thing to try is to whip out adb snd see what dun_tethering is set to. It has to be a 0 and not 1 or null.
8. But in further reading I can see dun which is basically hot spotting is all about having different networks. So in the old days hotspot traffic was carried on a second network. So a 0 means use APN 0 and 1 means 1. In the old days hotspot spot traffic was carried on a different network than regular data. This gave me an idea.
9. Xiaomi hyperos lets you add multiple APN profiles so I made two identical ones to cover whether dun is set to 0.
10. Then I read about APN profiles. And I added a “,dun” to the first one and it works! The history of this is that hot spots used to be a different price or not enabled so it was carried on a different network and disabled.
11. Once this was resolved, I can even plug a usb to Ethernet adapter in and use with my laptop!

Net, net, the Android APN defaults are wrong from US Mobile at least for the Xiaomi phone. The APN profile needs to explicitly say “dun” in it or it won’t enable hot spots

Decider ring for all this:

1. Dun. This is Dial up networking. Man that’s a blast from from the past. But this is data only hot spotting is.
2. APN (Access Point Name). This is basically the settings that are needed to operate on the network. It’s a mishmash of acronyms and about 40 years of cellular technology history. It is configuration information for all the non voice features of the network. Technically it’s the gateway between the mobile operators network and the public internet and the device provided.
3. APN name. This is a fixed field. So for US Mobile it is ereseller. There are whole lists of these they you can look up
4. MCC (Mobile Country Code). This is what nation your phone is accessing. It has to match the sim data. Confusingly these are not phone country codes. So the US network is 310, Germany is 262… because the because region 2 is Europe.
5. MNC (Mobile network code). This is the carrier so 260 is t-mobile USA and
6. ICCID (Integrated Circuit IDentifier) is the unique code of your SIM card as digits 5-7 so it should match the MNC. And hopefully gets set automatically. The digits are decoded as “MMC[CC] II[I]NN NNNN NNNN NN C x” where MM is always 89 for SIM cards, C[C[C]]is the country code so 1 for the US or 64 for New Zealand, III is for the issuer which is usually but not always the same as the MNC. 480 is for Verizon and 24 is for the:”degrees. You can usually figure out this variable grouping by counting backwards from the right because the account is fixed at 12 digits and the us a checksum. Alternatively just look for lots of zeros since most people haven’t used a trillion sims yet. Sometimes the country code is encoded as 01 by the way like with t-mobile but just 1 like Verizon. Confused yet. And they say it’s the same as the MNC but that’s not always true.
7. For US Mobile, it complicated. And historically be size of mergers one carrier can have lots. Wikipedia has a decent list of what’s operational and what isn’t.So that’s 410 for att (us mobile says also try 280 which is listed as att no operational but maybe for MVNOs?), Verizon is just complicated but it says use 480 for is mobile and MCC of 311 and not 310 but 311 is also allocated to the US and MNC of 480 which is listed as LTE only but Ruth’s so I think they are reusing it for MVNO operations. T-mobile doesn’t need any of this because the APN name is “wholesale” it old setup was MNC 310 and APN 260 (240 if that doesn’t with) which maps to the main t-mobile and then one that’s listed as not operational.
8. MMS Proxy and MMSC server url. This basically enables SMS to carry more than 140 bytes and is like traditional networking and changes depending on network
9. APN Type. The critical thing is it enables features as a comma separated string. Default is what it sounds like, but you add other fields to override and make super they are enabled. Some key ones: mmc to use multimedia on SMS, supl is secure user plane which means location services, dun is for hotspots and needed see above, hipri if you have multiple APN profiles will switch, fota is firmware updates over the air.
10. US mobile recommends “default,supl,mms,fota” and adding “dun” worked for me!
11. There are others I haven’t tried like: internet for web access, cbs for cell broadcast messages, xcap for remote device configuration, ia for initial attach, emergency for emergency services, ims for ip multimedia and yes I’ve no idea what these are. But I might try hipri and internet at some point.