internet sharing (mojave) AND two-way connection I apologize for any confusion bc of the subject line. Explanation:
I am sharing a wireless connection on a Mojave MBP 2012 (ethernet/thunderbolt/USB) with a PC running Win10. The PC is able to surf, so internet sharing is nominally working. Is there a way to also go in reverse? What I mean is, I want to use the same network to connect from the MBP to the PC, for example using Remote Desktop.
My hardware is configured as follows:
wireless router &lt;---&gt; MBP &lt;---&gt; eth &lt;---&gt;|        |&lt;---&gt; eth &lt;---&gt; PC
                                         8-port hub

For separate reasons, I'm not using the default internet sharing settings:
icu-mojave:~ $ ifconfig bridge100
bridge100: flags=8863&lt;UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST&gt; mtu 1500
    options=3&lt;RXCSUM,TXCSUM&gt;
    ether aa:20:66:b1:68:64 
    inet 192.168.22.10 netmask 0xffffff00 broadcast 192.168.22.255
    inet6 fe80::a820:66ff:feb1:6864%bridge100 prefixlen 64 scopeid 0xe 
    Configuration:
        id 0:0:0:0:0:0 priority 0 hellotime 0 fwddelay 0
        maxage 0 holdcnt 0 proto stp maxaddr 100 timeout 1200
        root id 0:0:0:0:0:0 priority 0 ifcost 0 port 0
        ipfilter disabled flags 0x2
    member: en0 flags=3&lt;LEARNING,DISCOVER&gt;
            ifmaxaddr 0 port 7 priority 0 path cost 0
    Address cache:
        84:2b:2b:a5:11:63 Vlan1 en0 1199 flags=0&lt;&gt;
        dc:a6:32:96:3f:b8 Vlan1 en0 1192 flags=0&lt;&gt;
        84:2b:2b:a5:11:10 Vlan1 en0 1187 flags=0&lt;&gt;
    nd6 options=201&lt;PERFORMNUD,DAD&gt;
    media: autoselect
    status: active

My ethernet interface looks like this:

As I mentioned, this &quot;works.&quot; The PC is surfing the internet etc - it is set up to get an address conventionally (DHCP) and has the IP 192.168.22.11.
Problem: from the MBP, I can't ping 192.168.22.11. I get a request timeout (as opposed to host down for example). I figure if I can't ping it, I can't do anything else either. For starters, I'd like to connect to the PC using Remote Desktop from the MBP so I can get rid of the extra monitor and keyboard.
OK that's it – is this quest even possible perhaps with a change to bootp settings, or do I need to replace the hub with a router and create a 2nd downstream network? I've read that Apple's NAT doesn't do &quot;true bridging,&quot; but I can't evaluate that comment or whether that's the issue even.
Answering my own question for the record if anyone else searches. FYI I had to go to a full router setup to get this to work. The new configuration is:
wireless router &lt;---&gt; MBP &lt;---&gt; eth &lt;---&gt;|    |&lt;---&gt; eth &lt;---&gt; PC
                                         router

The MBP side of the router is the &quot;internet&quot; connection and the other side is the 4-port hub provided by the router for its private local network. Had to set up port forwarding on the router to target individual PCs via RDP, and there are Raspberry Pis on the hub side as well, but all is functional.
I still think I'm lacking something because &quot;internet sharing&quot; is inherently 2-way on some level, but I don't know enough about Apple's implementation of this sharing to know what's missing.