Random ICMP NAT Issues in Teltonika Routers

NETWORKING SOLUTIONS
1

Hi community,

I am experiencing an issue with some Teltonikas (RUT 300 and RUT 956). The devices are installed in machines and they restart a couple of times per day. The issue seems to be a malfunction of the NAT in the ICMP protocol that goes from the LAN to the WAN. The occurrence is very random; it can happen as rarely as once a week or as frequently as twice a day. It happens only after the device has restarted and persists for a couple of hours before starting to work properly. Interestingly, the NAT works properly for the NTP protocol when the issue is happening.

I did some packet capture in the Teltonika using tcpdump, where I could see that the router didn’t change the IP source of the outgoing packet. In normal operation, it would change the source IP address to the WAN IP.

As it seems to be related to the firmware, we updated one of the RUT 956 devices to the latest mass production firmware version 7.11.3, but the issue still occurs.

The capture on the left side is when the issue occurs.

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5

Hello,

Apologies for a delayed response. Could you confirm if the initially described issue still persists with the latest 7.13.3 firmware?

Additionally:

  • Does this behavior occur when pinging from an end LAN device?
  • You’ve mentioned that it might be firmware related, have you noticed similar behavior on older releases?
  • Could you provide any further details, as the issue is hardly replicable?

Best regards,

6

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