Raspberry Pi + Telit LE910C4-NF: LTE attaches, gets IP, ping works, but TCP/ HTTP times out

Raspberry Pi Base HATs 3G/4G&LTE Base HAT
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1

Hi,

I’m seeing a persistent cellular connectivity issue with a Raspberry Pi using
a Sixfab 4G LTE HAT and a Telit LE910C4-NF.

Current behavior:

  • LTE registration succeeds
  • the modem attaches successfully
  • the cellular interface gets an IP address
  • ICMP ping works over the cellular interface
  • UDP DNS works at least to 8.8.8.8:53
  • but TCP/HTTP/HTTPS over cellular times out

What we already tested:

  • account is active and not over limit in Sixfab Connect
  • modem-side data session works
  • modem-side ping works
  • switched from ECM mode to QMI mode
  • re-enabled ModemManager / NetworkManager
  • QMI bearer comes up successfully and gets an IP
  • tested multiple public endpoints over the cellular interface
  • forced registration attempts on both T-Mobile (310260) and AT&T (310410)

Packet capture result:

  • outbound TCP SYN packets leave on the cellular interface
  • no SYN-ACK packets return

So at this point it does not look like an application bug on the Pi, and it no
longer looks like only an ECM-mode problem.

Has anyone seen this with a Sixfab SIM / Telit LE910C4-NF before?
Did you resolve it with a SIM/network session reset, carrier/profile change,
or something else on the Sixfab side?

I’m also opening a direct support case with Sixfab, but I wanted to ask here
in case anyone has seen the same pattern.

Thanks

7

Hello @mgwalkerjr95

To investigate this further, could you please provide the ICCID number(s) of the affected SIM card(s) to message option? This will allow us to check the SIM status, network configuration and any potential restrictions from our side.

Once we have the ICCID, we will review the setup and assist you accordingly.