I experienced a somewhat similar issue yesterday on my network that I described in detail here [0].
Essentially one of the computers (running ubuntu) on my network started sending a VERY high volume (it measured 20gb for the day, and I think it was all over a 10 minute period) of DNS traffic to my router, which runs an unbound instance for my network. That traffic (or at least I think it was that traffic) brought down my network to the point where I could even ping an external or internal ip address.
Does tcpdump show the destination ip address the traffic was sent to on AT&T's network? Curious if that could be a dns server..
Also, what version of ubuntu is your desktop running, and what software does it have on it? Are you using canonical's livepatch service?
Essentially one of the computers (running ubuntu) on my network started sending a VERY high volume (it measured 20gb for the day, and I think it was all over a 10 minute period) of DNS traffic to my router, which runs an unbound instance for my network. That traffic (or at least I think it was that traffic) brought down my network to the point where I could even ping an external or internal ip address.
Does tcpdump show the destination ip address the traffic was sent to on AT&T's network? Curious if that could be a dns server..
Also, what version of ubuntu is your desktop running, and what software does it have on it? Are you using canonical's livepatch service?
[0] https://forum.opnsense.org/index.php?topic=31284.0