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Thread: internet sharing with new(ish) mac pro intermittent (failing)

  1. #1

    Member Since
    Jul 06, 2018
    internet sharing with new(ish) mac pro intermittent (failing)

    I've had a 2010 big silver mac pro for a while and recently, very slowly, transitioned to a newer small black cylinder model. It works really well except for one thing.

    I have it in my office at home, and it gets a great wireless signal from the router in the kitchen downstairs. So did the silver one. I use internet sharing to connect my non-wireless work PCs in my office to the network. With the old silver one, it worked flawlessly for years. With the new guy, it barely works at all. Both were fully up to date software/OS wise with High Sierra. I have no idea what's going on. I've tried both ports, new cables (even though they worked fine with the silver one), new hardware on the PC side, and everything is pointing to the small black cylinder.

    It's a little weird, because it will sort of connect, and on the PC side, it shows an IP of, and a gateway of 2.1, which is basically what I had with the old one. On the mac pro, if I click on Network and Ethernet 1 (or 2, whichever is connected), I get Status Connected, but it says it has a self-assigned IP address and will not be able to connect to the Internet. IP of Now, maybe that's normal, but it seems odd and inconsistent, and not what the old one did.

    Even more weird, is that it actually is sort of connected. Some web pages will occasionally load, but the real indicator is ping response:

    my-Mac-Pro:~ me$ ping
    PING ( 56 data bytes
    Request timeout for icmp_seq 0
    64 bytes from icmp_seq=1 ttl=128 time=0.406 ms
    Request timeout for icmp_seq 2
    Request timeout for icmp_seq 3
    Request timeout for icmp_seq 4
    64 bytes from icmp_seq=5 ttl=128 time=0.488 ms
    Request timeout for icmp_seq 6
    64 bytes from icmp_seq=7 ttl=128 time=0.267 ms
    Request timeout for icmp_seq 8
    Request timeout for icmp_seq 9
    Request timeout for icmp_seq 10
    64 bytes from icmp_seq=11 ttl=128 time=0.581 ms
    64 bytes from icmp_seq=12 ttl=128 time=0.383 ms
    64 bytes from icmp_seq=13 ttl=128 time=0.413 ms
    Request timeout for icmp_seq 14
    Request timeout for icmp_seq 15
    Request timeout for icmp_seq 16
    64 bytes from icmp_seq=17 ttl=128 time=0.450 ms
    Request timeout for icmp_seq 18
    Request timeout for icmp_seq 19
    Request timeout for icmp_seq 20
    Request timeout for icmp_seq 21
    Request timeout for icmp_seq 22
    Request timeout for icmp_seq 23
    64 bytes from icmp_seq=24 ttl=128 time=0.451 ms
    Request timeout for icmp_seq 25
    Request timeout for icmp_seq 26
    64 bytes from icmp_seq=27 ttl=128 time=0.543 ms
    64 bytes from icmp_seq=28 ttl=128 time=0.607 ms
    64 bytes from icmp_seq=29 ttl=128 time=0.438 ms
    Request timeout for icmp_seq 30
    64 bytes from icmp_seq=31 ttl=128 time=0.525 ms
    Request timeout for icmp_seq 32
    Request timeout for icmp_seq 33
    64 bytes from icmp_seq=34 ttl=128 time=0.554 ms
    --- ping statistics ---
    36 packets transmitted, 13 packets received, 63.9% packet loss
    round-trip min/avg/max/stddev = 0.267/0.470/0.607/0.090 ms
    my-Mac-Pro:~ me$

    I've been working with computers and networking for a long time, and I've never seen such consistently erratic behavior.

    Did a bit of googling and binging and found nothing other than howtos and really old discussions on this site. I'm hoping someone here has some ideas. Thanks.

  2. #2

    MacInWin's Avatar
    Member Since
    Jan 01, 2009
    Winchester, VA
    What other transmitters do you have near the router or two Macs? iPhones, iPads, wireless phones, bluetooth devices, home automation, remote controls, etc, all radiate and with all those signals in the air, can heterodyne together to mess up packets over WiFi. Try moving some of any that might be nearby.

  3. #3

    joelw135's Avatar
    Member Since
    Oct 20, 2008
    You can try changing your WiFi channel, as certain other devices interfere with transmission. I know in my case it is my home automation equipment.

  4. #4

    Member Since
    Jul 06, 2018
    So I don't think the problem is the wireless. That's working just fine. It's the connection to the PC over ethernet that isn't solid - see the ping results above. There's something very wrong with the internet sharing on this computer.

  5. #5

    MacInWin's Avatar
    Member Since
    Jan 01, 2009
    Winchester, VA
    OK, the IP number starting with 169 will never connect to the internet, as it's an internally assigned number. Open System Preferences, Network, click on the interface of your choice (wireless or ethernet) and then if it's Ethernet, there is an entry for "Coinfigure IPV4" in the window. Pick "Using DHCP" and then Apply. For WiFi, Select Advanced, then TCP/IP and make the same choice for "Configure DHCP." Click OK and then Apply.

    Now your Mac will look to the router for an IP number and should work well.

  6. #6

    Member Since
    Jul 06, 2018
    I think I didn't explain it very well the first time. My wireless connection to the router is fine. This works perfectly for all wireless devices in the house, importantly both the old and new mac pros. I can connect, stream video, play games, download stuff, browse the web, all uninterrupted from the new mac pro.

    The problem is on the ethernet side that the new mac pro is sharing with the PC. The mac says the IP address is 169 on the ethernet interface. The PC says it's 192. They can ping each other on the 192 with a 30-40% success rate. This exact setup worked perfectly for years with the old mac pro. Not so much with the new one. I don't understand how the mac pro can see the 192 network with the self assigned 169 interface. That alone is messed up. The fact that it doesn't really work confirms it.

    More to your point, both interfaces are configured for DHCP. I wonder if I set the ethernet manually if that would work better.

  7. #7

    Member Since
    Jul 06, 2018
    So, it just got weirder.

    I manually set the IP on the Ethernet side. I went with Plugged in the Ethernet to the PC. Bam, it's online instantly. All good, right? Nope. The PC has I cannot ping this from the mac pro. Ethernet shows green and connected. The PC is connected, everything looks good, so who cares about the mac pro Ethernet weirdness, right? Nope. My mac pro, despite showing 5 bars, green and connected on Wi-Fi, is actually not connected to the network. I cannot do anything with any network, Ethernet or Wi-Fi, though they're both green and connected.

    So, PC problem solved, but now the mac pro doesn't work, and is showing status inconsistent with the behavior. This network sharing is really messed up.

  8. #8

    MacInWin's Avatar
    Member Since
    Jan 01, 2009
    Winchester, VA
    I know you said, "I've been working with computers and networking for a long time, and I've never seen such consistently erratic behavior." But I am going to take a step back and do some explaining on how your router should work and why what you've done is not working. My apologies if you already know what I'm about to say.

    Your ISP assigns ONE real internet IP to your account, and that IP number may change as the ISP sees fit to do so. Your router sees that IP number on the Internet side and responds/reacts to it appropriately. On the other side of your router, the router issues IP numbers in a range, usually either in the 192.168.x.x or 10.10.x.x. range. Never both. You can tell which the router is using by looking at the router itself from your local area net side. Try logging into either or and see under the DHCP setting how the router is working.

    Now, all the devices in your home network ask the router for an IP under DHCP unless you manually assign one. They will then be issued a number in the format 192.168.x.x or 10.10.x.x, depending on the defaults in the router setup. But one router will never issue BOTH 192.168.x.x and 10.10.x.x numbers. It's either/or.

    For manually assigned numbers, you set the IP in the device yourself ON THE DEVICE. But then you have to tell the router NOT to assign that same number to anything else because it doesn't know you've already assigned it to something. Most of us (99% ?) just let the router assign numbers and get on with more important things. I have occasionally had to assign a fixed IP number for a shared LAN printer, or a shared Network Accessed Storage system (NAS) if I have issues with "dumb" software that demands that it have an IP number instead of a device name in order to share. But that's rare, and becoming more so as manufacturers are making smarter and smarter devices. If you HAVE to do that, make sure the number is in the same range as the one's being assigned by the router. So if the router is issuing 192.168.x.x numbers, I would make the one I had to assign something like 192.168.x.254, then tell the router NOT to use that number.

    So, what I suggest is that you find out which range of numbers your router is issuing (I think it's in the 192.168.x.x range based on what you've said already) and then get EVERY device to use DHCP to get a number and let the router do the work with you.

    The reason you cannot share between 192.168.x.x and 10.10.x.x is that they are in two different ranges. You can communicate between them, but the devices think they are in different networks, which eliminates sharing. The router keeps something called a "subnet mask" that it uses to determine which devices are in the same subnet. The subnet masks between 192.168.x.x and 10.10.x.x are different, so not the same subnet.

    Hope that helps a bit.

    EDIT: Oh, and if the WiFi gets a 192.168.x.x number from the router but you've assigned a 10.10.x.x fixed IP to the Ethernet, you have your Mac Pro in two different networks and it can't even talk to itself! My MBP is connected to both Ethernet and Wifi so that I get the high speed of Ethernet but the ability to use my Apple watch to unlock the MBP over WiFi. And both IP numbers come from the router that is the DHCP server.

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