It’s me again. I have a network issue I can’t figure out.
I have an Unraid server setup that’s been working perfectly fine for nearly a year without issue. I am on AT&T Fiber with their HUMAX BGW320-500 router. The server is assigned 192.168.1.10. Earlier this week the AT&T router went ballistic and dropped connection and rebooted several times in a row in the evening. After that, I am unable to access the Unraid server from any device on the network.
What I have done:
Unplugged network cable(s) from server in attempt to let the port reset itself. Unplugged from 8-port switch thinking it locked the port. Moved connection to another port on switch. None of this worked.
I had the server in bonding mode with 2 network ports, so I removed the bonding and rebooted, still nothing.
Moved the server connection directly to the AT&T router, still nothing.
I CAN ping the server address from the router’s built-in diagnostics/ping/tracert page, so it has a connection and is visible to the router.
From my desktop PC, I released and renewed the IP thinking maybe the DNS table had gotten confused. No luck there. Did a manual ipconfig /flushdns with no luck.
The server can ping the router address, but nothing else on the network.
It feels like the router just decided there is no routing table or way to route to the server from any device EXCEPT for the router itself. I’m really attempting any option without a factory reset on the router , I really don’t want to go around the house and reconnect everything … again.
Any ideas?
Well, just shoot me.
After leaving the server off for several days, then randomly deciding to reboot the router again, it works 
Why does the problem always fix itself after i post something?
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Looks like a factory reset of the router is in order, despite your unwillingness to do so. Having said that, the router should have an option to download its config to your PC. After the reset it should be able to reload said config file (probably a text file of sorts) to the router to restore the previous situation. You could even download the factory-default config to compare against your current config. That is, as long as it’s actually a text file.
OK, here’s why: the router dishes out IP addresses and those have a best-before date (TTL: time-to-live). After that period the DHCP server assigns a new IP address, or a new TTL period, to a network interface, based on its MAC address.
Unfortunately, saving the config isn’t an option, it literally doesn’t have the option to save it anywhere except “at AT&T”. Had an issue late last year where their firmware update would randomly bork custom settings and AT&T had to remote in and factory reset, and even though they said that their system backs up the the custom configs, it doesn’t, and there is no way to do it locally either.
The Joys of being on fiber without the option of buying my own hardware to run it …
This type of behaviour can happen when two machines have the same IP address. It might seem random which machine with duplicate IP will work because it depends on which one sends the ARP reply the quickest, or which ARP reply is cached the longest.
That can happen if the DHCP server (on the router, in most home networks) has a corrupted state, or you’re mixing DHCP hosts and static hosts.
In that case i’d try to reset the router’s DHCP state and all the DHCP clients states. On Windows ipconfig /release + ipconfig /renew should do that. Alternatively just use static IP addresses, if you’re not changing network config/topology often.
If possible in the router, change the DCHP IP range it can hand out to something like 100-254. Many home routers come configured for the entire IP range which is bad if you want static IPs on some devices. Setting it higher lets you know the high range is a DHCP address and anything below .100 is a static.