Why was my full node knocked off the network last night? Any idea what happened last night that caused my full node to fail with messages like this:   (full log available upon request)


2017-09-25 21:15:59 Bitcoin version v0.15.0.1
...

2017-09-25 21:32:33 UpdateTip: new best=00000000000000000079fb649dd2c7e35978bd6d7922b8661c1e3ae597f24191 height=486858 version=0x20000002 log2_work=87.166038 tx=256852323 date='2017-09-25 03:51:56' progress=0.999233 cache=370.8MiB(2762033txo) warning='2 of last 100 blocks have unexpected version'
...
2017-09-26 13:32:19 receive version message: /bitcoin-seeder:0.01/: version 60000, blocks=350000, us=108.196.200.233:8333, peer=2183
2017-09-26 13:32:52 receive version message: /Bitcoin ABC:0.14.4(EB8.0)/: version 70015, blocks=489424, us=108.196.200.233:8333, peer=2184
2017-09-26 13:32:55 ERROR: AcceptBlockHeader: Consensus::ContextualCheckBlockHeader: 000000000000000000639be19a0123a1c99d9fef89f0b8ac055a77f4ef86ae3b, bad-diffbits, incorrect proof of work (code 16)
2017-09-26 13:32:55 Misbehaving: 10.32.0.1:55716 peer=2184 (0 -> 100) BAN THRESHOLD EXCEEDED
2017-09-26 13:32:55 ERROR: invalid header received
2017-09-26 13:32:55 ProcessMessages(headers, 162003 bytes) FAILED peer=2184
2017-09-26 13:32:55 connection from 10.32.0.1:46684 dropped (banned)
2017-09-26 13:32:59 connection from 10.32.0.1:47442 dropped (banned)
2017-09-26 13:33:00 connection from 10.32.0.1:50695 dropped (banned)
2017-09-26 13:33:00 connection from 10.32.0.1:49700 dropped (banned)
2017-09-26 13:33:02 connection from 10.32.0.1:15754 dropped (banned)
2017-09-26 13:33:03 connection from 10.32.0.1:47560 dropped (banned)
...
...

At this point my node was seen as &quot;down&quot; by https://bitnodes.21.co/
Today, it appears to be working normally again.
As Nate Eldredge said, the block that you received is a Bitcoin Cash block which is invalid to Bitcoin Core. Because of this, your node banned the Bitcoin Cash node that sent you the block. However, it seems like the way that you have your node set up is that the gateway is acting as a proxy instead of passing through the connections. Thus Bitcoin Core thinks the connection came from your gateway instead of from where it actually came from. When your node banned the Bitcoin ABC node, it banned your gateway as it thought that was the bad node. This had the effect of then banning everything connected to you because they all connect through that gateway and the gateway was banned. The connections are back today because the ban is only for 24 hours.

I highly suggest that you make sure that the connections are properly being passed through so that this does not happen in the future. To ensure that they are passed through, if you use getpeerinfo (or the Peers tab of the Debug Window if you are using the GUI) and look at the IP addresses of all of the nodes you are connected to, they should not be the IP address of your gateway.