FYI, there are no nVidia-specific files for networking. The Realtek drivers are mainstream kernel, network setup is mainstream Ubuntu. So far as router issues go, caching is why they fail on some ports but not others…no matter how many devices the router works with, cache has a bad tendency to get in the way on routers that are never rebooted. In the original case of this thread there was also a link failure, which is indicative of physical connection (beyond software). Does your link light fail to go on when network fails?
It is possible for some of the network setup from JetPack to be incorrect, but JetPack uses standard Ubuntu interfaces for this. JetPack may not be aware of any special setup required, e.g., firewall configurations or other custom authentication (e.g., SSL/TLS certs).
NSS is related to anything looking up “names” (network, password, etc). This could cause an issue, but dotted-decimal addresses should show up for ping and ssh when requests use a dotted-decimal address (the “x.x.x.x” format, as opposed to a name). Having 127.0.1.1 and 127.0.0.1 is correct for local host loopback, but having nothing pointed at your outside network is an issue…none of the 127.x.x.x addresses are remote host. The loopback will be associated with interface “lo”, while a real ethernet will be listed as something like “em0”, “eth0”, so on (via ifconfig).
Routers generally clear cache via reboot. Caches have complicated rules for re-use and clear. Limited memory means caches can fill up even with small numbers of DHCP users. Again, this is almost always fixed by reboot since cache memory is all cleared.