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  1. #1
    Networking - Sierra DHCP Issue

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    Networking - Sierra DHCP Issue
    So my router is setup on 192.168.1.1 on this iMac


    I know this from the couple of devices connecting to it on the network. And also I set it up this way (from the default 192.168.0.1).

    Yet when I boot my iMac it sometimes picks up on the ethernet cable, 192.168.88.1


    I have to go into the Network Preferences. Set Configure IPv4 to to Off. Apply. Set it back to Using DHCP. Then Apply again.

    This can't be something that I have to watch out for on every reboot. So what can I do to stop this behaviour?

    As an aside, I have a bootcamp install that when was working didn't have this problem. I also have a Linux install via an external drive that never has this issue.
    Attached Images Attached Images
    Last edited by milomak; 07-21-2017 at 07:14 PM.

  2. #2
    MacInWin
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    If your Mac is getting 192.168.88.1 from the DHCP server, the problem lies with the DHCP server. Note on your screenshot that the router thinks it's at 192.168.88.1, and has two DNS servers, one at 192.168.88.1 and one at 192.168.1.1. So, for whatever reason, the router is set up for DHCP to assign addresses in the 192.168.88.x range, which it is quite properly doing.

    Now, the router MIGHT be set up to assign 192.168.1.x over Ethernet, but 192.168.88.1 over WiFI, which would mean that if the iMac ever has the WiFi turned on, it gets an IP in that range, the network is happy, the iMac is happy and all is well. But then you turn off WiFi and somehow the IP remains set at 192.168.88.x, but still connects over Ethernet to the router, which sees the address as "fixed IP" and just deals with it. That's all theoretical, of course.

    What I would do is log into the admin account on the router and check the DHCP settings to see what IPs are being assigned on both Ethernet and WiFi.

    Finally, it *might* be that the MAC of the iMac hardware is associated in the router with one IP when on Windows, one on Linux and one on macOS. If the router ignores the DHCP request for a new IP and assigns the same one to the MAC hardware address, then you might fall into this mess. Again, look at the admin function of the router to see what IP range is approved for assignment.

    And finally, finally, do you ever use WiFi on the iMac and do you have neighbors? I ask because one of them may be in the 192.168.88.x range and your iMac is connecting to them, not your own router. It's happened before...

  3. #3
    Networking - Sierra DHCP Issue
    harryb2448's Avatar
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    What are your DNS Server settings? Can't be as shown.
    Using OS X.7 or later make a bootable USB thumb drive before running Installer!

  4. #4
    MacInWin
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    Actually, Harry, DNS could be as shown. If the modem to the ISP has set within it a set of DNS servers (and most do), then when the search at the 192.168.x.y fails, as it will, then the modem kicks in and passes the request to its DNS server and up the line. Not terribly efficient, but it would work.

  5. #5
    Networking - Sierra DHCP Issue

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    This is an issue related to Sierra (wifi off) as no other device on the network has this issue.

    And as I stated, I have a Windows install (Bootcamp) and Linux (external drive) and they have no issue with connection

    I guess it wants me to specifically set the DNS Server
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  6. #6
    Networking - Sierra DHCP Issue
    lclev's Avatar
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    I am going to take a wild guess here... is the TP-Link wireless ip address set to 192.168.1.1 and the wired settings set to 192.168.88.1 ?????? I guess I am totally confused as to where the 192.168.88.1 is coming from???

    Also in the router's DNS settings what happens if you use 8.8.8.8 and 8.8.6.6 - these are free DNS Google servers.

    Next question - what happens if you force the iMac to have manual settings?

    The iMac is getting the wired settings from somewhere and the TP-Link settings listed do not even remotely resemble the settings shown for the iMac wired settings.

    Confused here.

    Lisa
    Recommend using Onyx to clean your Mac.
    If you have been helped, please add to their reputation by clicking on the icon in the lower left hand corner of the post.

  7. #7
    MacInWin
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    I'm with you, Lisa. The 192.168.88.1 is coming from somewhere. It cannot be just random, and it's NOT endemic to Sierra, or there would be howls from the universe. I have both interfaces in my MBP, and the two addresses are: WiFi, 192.168.1.4 and Ethernet is 192.168.1.18. The two operate cooperatively, so nothing strange happens. But what I do see in the DHCP settings is that the default gateway is 192.168.1.1. That almost implies that there is a second DHCP server somewhere in the network, and I'm wondering if it is the cable modem or whatever the ISP provides to connect to the outside world. The 840N, according to the TP-Link guide, is NOT a modem, just a WiFI router, so I wonder if the ISP's modem is also a router and if the address range set there is in the 192.168.88.x range? if the Ethernet is connected to that modem, there could be a conflict between that DHCP server and the DHCP server in the TP-Link.

    So, milomak, is that a possibility? The setup should be that the ONLY thing connected to the modem from your ISP should be the one ethernet cable from the modem to the WAN port on the TP-Link, and all other Ethernet connections would need to be to the TP-Link ethernet sockets.

  8. #8
    Networking - Sierra DHCP Issue
    pm-r's Avatar
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    If the modem to the ISP has set within it a set of DNS servers (and most do), then when the search at the 192.168.x.y fails, as it will, then the modem kicks in and passes the request to its DNS server and up the line. Not terribly efficient, but it would work.


    Is not the "192.168.x.y" a bogus and basically a nonworking address that Bill Gates originally setup for some bogus network testing type address that's still in use??

    And basically means you're not going anywhere and not connected to any external internet access point???

    EDIT:
    This would be typical I believe:
    "A private IP address (192.168.x.y) means you are not getting your IP address from us. If you still have a private IP, it is possible that it is coming from another person's router - this is known as a rogue DHCP. "
    https://www.uoguelph.ca/ccs/internet...dress-192168xy







    - Patrick
    ======
    Last edited by pm-r; 07-29-2017 at 11:33 PM.

  9. #9
    MacInWin
    Guest
    Patrick, the 192.168.x.y range of IPs is a clever way to solve the issue of multiple addresses in a small network but a limited number of IP numbers worldwide. Basically, the router in your home has two IP numbers. One it gets from your ISP and is in a range of numbers assigned to your ISP provider by the managers of the Internet, ICANN. The other is in a range either starting with 10.x.y.z or 192.168.x.y and is controlled by the DHCP server in the router. Basically, the router shares the one IP from the ISP with all of the devices in the network the router manages by mapping their 192.168.x.y IP number onto that external number, then when a response comes back from the Internet, it routes the response to the appropriate 192.168.x.y device within the local network. From the article, the University of Guelph apparently has it's internal network set up with a range of IP numbers and does not use the 192.168.x.y standard internally. That's ok, as long as the University isn't using rogue IP numbers that someone else in the universe has paid for through ICANN. EDIT: So, the University is saying to users that if they have an IP of 192.168.x.y, it didn't come from the University and their computer is NOT connected to the University LAN directly. It still could be connected through the university network if the DHCP server that provided the IP 192.168.x.y is connected to the University LAN, which is why they called it "rogue."

    There is nothing "magic" about either 10.x.y.z or 192.168.x.y. In fact, if you wanted to, technically you COULD set your own home network up with any IP range you wanted to. But if you then venture out into the Internet, you have to play by the rules of ICANN and not use those internal numbers because they may interfere with someone else's network assignments.

    But the "custom" is to have 10.x.y.z and 192.168.x.y to be the ranges used "inside" the modem from your ISP.

    As far as Bill Gates, I don't know anything about his involvement in the selection of that range. Here is some information from the Internet search engine, WhoIs:

    https://www.whois.com/whois/192.168.0.1

  10. #10
    Networking - Sierra DHCP Issue
    dtravis7's Avatar
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    Pat, I have been using 192.168.1.? since my 1st router in 2001 and never had any issues. those addresses are for the Local Network (LAN). Otherwise everyone could find Ľour IP if Ľou used no router with DHCP.

    Some routers have the LAN with DHCP out of the box at 192.168.0.1. Both work the same. I just got used to the one I use. Some routers use the 10.?.?.? IP for the LAN.

    To the OP, I have never had one issue with Sierra getting an IP from any router in my house and I have many and I have been running Sierra since the very first Beta.


    I bet it's something with that TP-Link router.

    Do you have a Modem/ Router from your ISP besides that TP Link?
    Last edited by dtravis7; 07-30-2017 at 05:05 AM.

  11. #11
    Networking - Sierra DHCP Issue
    harryb2448's Avatar
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    And I have no issues, ethernet or WiFi, with a TP-Link W7980 router and 192.168.1.1 being the address and the IPv4 address is 192.168.1.100 so that is in common. The one I don't see is the one endiung in 247.

    With Sierra both the 5GHz and 2.4GHz channels both work perfectly, the latter for an Epson WiFi printer.
    Using OS X.7 or later make a bootable USB thumb drive before running Installer!

  12. #12
    Networking - Sierra DHCP Issue

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    Guys. It is not the router because none of many other devices have this issue.

    Even on the iMac. it is specifically an OSX issue (not Windows or Linux which connect without issue on the same machine).

  13. #13
    Networking - Sierra DHCP Issue
    dtravis7's Avatar
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    I told you above I tried Sierra from the first beta on every Mac in this house and on many routers here and never have ever seen that issue nor read about it in the reports to Apple we all send in while testing.

    If there was such an issue with Sierra someone would have reported it long ago.

    Not sure what More I can say. Either that or there is some setting that we are not shown in the screen shots you shared. Out of the box Sierra has never done that.

    Are you sure that is Sierra and not High Sierra? Click on the Apple in the upper left corner and on about this Mac. What version does it say the OS is? Sierra is not OSX but Mac OS.
    Last edited by dtravis7; 07-30-2017 at 11:14 AM.

  14. #14
    Networking - Sierra DHCP Issue
    pm-r's Avatar
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    Quote Originally Posted by harryb2448 View Post
    And I have no issues, ethernet or WiFi, with a TP-Link W7980 router and 192.168.1.1 being the address and the IPv4 address is 192.168.1.100 so that is in common. The one I don't see is the one ending in 247….


    It seems one can have only a maximum of 254 hosts and I didn't realize that there are THREE groups of address that are commonly used:
    Together with the Internet Assigned Numbers Authority (IANA), they have reserved three “blocks” of the IP address space for private networks:

    10.0.0.0 – 10.255.255.255 (Class A)
    172.16.00 – 172.31.255.255 (Class B)
    192.168.0.0 – 192.168.255.255 (Class C)
    http://trendblog.net/ever-wondered-u...ddresses-home/



    EDIT:
    And a good eye harryb cause this also says and agrees it ain't gonna work:
    192.168.88.247 - IP address is in private non-routable range.
    Private IP Address Ranges

    Address ranges below are reserved by IANA for private intranets, and not routable to the Internet.
    For additional information, see RFC 1918.
    10.0.0.0 ~ 10.255.255.255 (10.0.0.0/8 prefix)
    172.16.0.0 ~ 172.31.255.255 (172.16.0.0/12 prefix)
    192.168.0.0 ~ 192.168.255.255 (192.168.0.0/16 prefix)
    https://www.speedguide.net/ip/192.168.88.247




    - Patrick
    ======
    Last edited by pm-r; 07-30-2017 at 12:20 PM.

  15. #15
    MacInWin
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    And a good eye harryb cause this also says and agrees it ain't gonna work:
    Patrick, it works because the modem between the ISP and the router map the internal IP numbers to the external IP the modem has gotten from the ISP.

    Take a look at this image from the User Guide for the OP's modem:
    SmallerLAN.png

    Note that the Internet is connected to the router through the modem (in the image it is listed as an ADSL modem, but could be any modem). That modem obtains an IP from the ISP that will be in the range that the ISP has negotiated with ICANN to use and will be unique to that one modem in all of the internet. The Modem connects to the router through the "Internet" port on the router. Internal to the router, that port is mapped by the DHCP application in the router to the devices attached to the router through the other Ethernet ports and by wireless. The router has the self assigned LAN address of 192.168.1.1, then assigned other numbers in the 192.168.1.x range, from 0 to 255 (256 possibles) to any device attached to it. As traffic flows through the router from the devices in the LAN, the router maps the packets based on the internal number to the devices in the LAN, and translates the packet to the external IP that the modem has obtained from the ISP. When that traffic hits the internet, it looks like it came from the IP of the modem, not the internal IP of the computer.

    For an example, in my setup I have Comcast as my ISP and I have a Comcast modem that has obtained the IP number from Comcast in the range 73.152.x.y, and with DNS of 75.75.75.75 and 75.75.76.76. That's the EXTERNAL network information. The Comcast Modem is connected to a Netgear Orbi router system. My INTERNAL LAN information from that Orbi is that my MBP has 192.168.1.18 as an IP, with the router identified as being at 192.168.1.1 and the DNS server being 192.168.1.1, plus a manually set 8.8.4.4 and the Comcast DNS of 75.75.75.75. I didn't set any of that except the 8.8.4.4. Otherwise it all came from the negotiations between the ISP, through the modem and the router. And the IP for the Ethernet port was negotiated between the Orbi and the MBP to avoid any other device in the LAN (If two devices have the same IP, communications will be confused and won't, in most cases, work at all.)

    As for being "non-routable" as the article you linked to said, that is true IF one were to manually assign an IP in the range 192.168.x.x to a device and then try connecting directly to the internet. Because 192.168.x.x (and the others) are defined as being INSIDE a LAN and ISOLATED from the Internet by a modem/router setup, the Internet does not route those addresses. Hence, the need for the modem to have an IP that is routable, i.e., one that ICANN has approved for use.

    So, it works. Now, if you have just ONE device in a home, and connect it directly to that modem from the ISP, then the number of the ISP router will be your IP number and your computer will be directly connected to the internet with that number. But if you have a router that supports DHCP and are connected to it, and not the modem, then you will have a number in the non-routable range as the IP in your system.

    In all of this discussion I've separated the modem and the router into two devices, as the diagram shows. Technically, the modem and router can be merged into one device, but the functions are the same for the two "parts" of that single box. In fact, in my system the modem from Comcast is a modem/router and I have put it in a mode to kill DHCP in the ISP box (called bridge mode) to allow the Orbit to assign all IPs in my network. LANs should have one and only one DHCP server or the communications will be confused and not work well, if at all.

    For the OP, the fact that you have two sets of IP ranges means there are two DHCP servers somewhere in your system. There can be no other explanation. It is NOT macOS, unless your system has been tweaked somehow to self-assign the 88 range. It's not a bug in Sierra, or there would be thousands of loud cries in the Apple universe about it. The single logical explanation of the setup as you have described it and as shown in the images you have posted is that somewhere in your network is a DHCP server that is issuing IPs in the range of 192.168.88.x.

    Is your modem from the ISP a true modem-only device or, like mine, a modem/router combo? If so, is it in bridge mode? It may be the source of the 88s. The fact that no other device has the issue is probably just coincidence at this point. Once devices get an IP from the DHCP server, they tend to hold that number unless something interrupts the LAN and forces it to change. So they may have gotten a valid IP from the DHCP server in the router but the upgrade to the Mac caused it to get an IP from the modem instead. That *could* happen if for an instant the default of 192.168.1.1 was set in the Mac, so it passed through the server to the modem, which assigned it's own set of IPs for that one device. The DHCP server should NOT have done that, but since it is on 192.168.1.1, the duplication of that number could have caused confusion and allowed the Mac to directly connect to the modem. That scenario is a really unlikely stretch, I do admit. What is much more likely is that something in the network is acting as a second DHCP server and using the range of 88.

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