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4G router - connection disappearing after a while, and keep-alive suggestions

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I have an embedded target going online via a RUT240 4G modem/router.

The RUT240 config is straight out of the box, latest firmware, factory defaults. It is a DHCP server for my board ( or some such) and via the Vodafone SIM card it goes online nicely and basically all works. It is a NAT router, like all the other standard (ADSL etc) ones. It has a fantastic array of features but a) most of them aren't needed and b) I am pretty sure some of them don't actually work (par for the source for a chinese linux box).

I have it sitting there, and my board is pinging every hour.

It works for hours or even days but eventually the connectivity is lost, until the RUT240 is power cycled.

Can anyone guess what might be happening?

I know that a GPRS/3G/4G network closes the connection after (IME) 180 secs. I found this out when trying to implement VOIP on a phone, supporting incoming calls (various hacks for that have been developed e.g. STUN). But here we are going freshly online every hour. And the GSM+4G signal is strong.

I am thinking that one needs a keep-alive process, which pings some URL say every minute. The data used up will be tiny and irrelevant and anyway even PAYG SIMs have a huge data allowance nowadays. Any real application of this will use a CONTRACT SIM anyway. Can anyone suggest what site or address to ping? I reckon pinging the default gateway ( or some such) will not do anything because it won't bring up the 4G. Could one just send a UDP packet to - in this case it could be a DNS request for

Can anyone recommend a good reliable 4G router?

The RUT box has no support - just yet another "forum" :) And I don't think it is reliable.

I'd think most of this stuff is Chinese made anyway.

The simplest solution is a timer socket repowering it once in a day. You may look at Mikrotik products for a reliable router.

Not wishing be the tin foil hat guy today, but this..

--- Quote from: peter-h on December 25, 2021, 07:55:45 am ---4G modem/router.

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--- Quote ---Can anyone guess what might be happening?

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It's no mistake that a time-based auto reset setting isn't included in the firmware. For that matter a setting for maintaining a persistent connection.

--- Quote ---Can anyone suggest what site or address to ping?

--- End quote ---
I had problems with a terrible ADSL router refusing to keep a connection or at least start a new one. I had a server box laying around and I made a script go grab random live web cam JPGs. The nearby house security system had a relay port that the script used to power cycle the router. Just awful.

That was a fair while ago and I doubt there are too many webcams that offer up small still pics anymore. And I would warn that exposing your IP to such things for that purpose may attract attention on your network you mightn't want.

What about a bit of server space somewhere offsite? It could send a ping to your network or vice versa and a do a horrendous raspberry pi power control solution that actives when it doesn't receive enough chirps from the offsite server.

Use the server space and encrypt and store some of your important stuff and solve the offsite backup predicament as well!


--- Quote from: peter-h on December 25, 2021, 07:55:45 am ---Can anyone guess what might be happening?

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Shitty software.

--- Quote from: peter-h on December 29, 2021, 08:02:26 am ---Can anyone recommend a good reliable 4G router?

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Depends on your budget. For remote units you don't go near a lot, use an EWON Cosy or Tosibox.
However, these are quite high up in price. But worth it. They do work reliably and safely and behind any CGNAT.

If that's too expensive you have to pay with some learning and time. You can use Mikrotik WAP LTE kit.
The also have more robust version with multiple sim for failover and such.
The software won't crap itself, if you lose connection you can configure the netwatch to reboot it. Or run custom scripts.
You can have it do many more things, but you have to put in some effort, because it's not a TP-Link click&config.
Very capable units for a low price.


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