**Edit- Sorry, I just tested this out without being attached to my Cox modem at all and I'm still experiencing the same gateway issues when I enable IPv6 on my nic. So I don't think it's a Cox issue.
OK - so something extremely weird happened to me yesterday. All of a sudden I found myself on a 10.0.1.1 subnet for no apparent reason whatsoever. I was still sitting behind my router and hadn't changed a thing, yet somehow I was on 10.0.1.1 with DHCP lease of 10.0.1.17.
My normal gateway is 192.168.1.1 and I have a statically reserved IP in my router of 192.168.1.2 for my main PC, so somethigng very strange was up.
I'll make a long story short, I thought my router had finally bit the dust, so I brought out a spare tonight, configured it and reconnected it, and all was well. For about 10 minutes. Then I found myself back on the 10.0.1.1 gateway. WTH. After some digging and hair pulling I noticed that I was being assigned an IPv6 address as well as IPv4. Having never seen this before I went into my NIC, disabeled IPv6, did a release/renew on my IP and bam, I was instantly back on my own gateway.
So I don't know much about IPv6, but I'm guessing it trumps IPv4, and somehow the NIC on my main PC is being assigned an IPv6 address from Cox and routing traffic through that. I turned on IPv6 on my NIC, did a release/renew, and I was back on 10.0.1.1.
I can't tell if there's some misconfiguration in my router or what, but this is about as far as my troubleshooting prowess will go. If anybody else has any other ideas please let me know. Right now I've got to go into all of my PC's/devices and disable IPv6 to get them back up and talking to my gateway.
The proof is in the screenshots so take a look:
With IPv6 turned on:
With IPv6 turned off:
Not sure if there's any correlation, but my modem recently started bonding 3 upstream channels as well: