Thanks, but I got into trouble with this perhaps because I don't understand the intent of this setting. So by default it looks like:
[5] --> Unban PrivateIP | [Enabled]
And when this is selected we get:
Select Filter PrivateIP Option:
[1] --> Enable
[2] --> Disable
These 2 setting levels seem contradictory. "Unban PrivateIP | [Enabled]" suggests private IPs cannot be banned whereas "Select Filter PrivateIP Option" (enabled) suggests the opposite. So which is it - do we want enabled or disabled? Neither of these work. The default "enabled" allows banning and the ban is listed via the web interface, but it doesn't actually "ban" the IP which still is shown on arp-scans and responds to pings. So I foolishly tried "disabled" which not only doesn't work neither, but it had the catastrophic effect of knocking my wireless repeaters offline (there's a serious bug somewhere - either in Skynet or the asuswrt-merlin firmware). I was sweating blood as I thought the router got bricked? Fortunately I regained control via a router lan port and recovered the network by rebooting the repeaters. Bottom line though is that this rogue IP is still not blocked and I'm getting nervous about having been hacked.
What am I trying to block/mute? This obscure IP which I can't correlate to any of my hardware started showing up on the RT-AC68U client list and on arp-scans:
192.168.1.184 SHENZHEN BILIAN ELECTRONIC CO.,LTD
I did some research on this and the claims are that this is generated by common networking hardware which just isn't identifying itself correctly. I've got issues with such assertions. Whatever this is it obtains its IP via DHCP. And all my wireless devices are already accounted for. It also creates an entry in the routing table, why?:
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.1.184 RT-AC68U-A448. 255.255.255.255 UGH 3 0 0 br0
And a nmap scan shows:
PORT STATE SERVICE
6668/tcp open irc
FWIW, I tried the suggestion given earlier in this thread of using the Network Services Filter. This has the effect of hiding this IP from the RT-AC68U client list and now it rarely appears on arp-scans, but it still responds to pings so it's still camped onto my network. Unfortunately out of sight is not out of mind. I was hoping Skynet would be my savior. Oh well. Looks like I may be getting my hands dirty with iptables and wireshark.