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Apple Computing Products:
macOS - Operating System
Networking - Sierra DHCP Issue
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<blockquote data-quote="MacInWin" data-source="post: 1764660"><p>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. </p><p></p><p>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.</p><p></p><p>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.</p><p></p><p>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.</p><p></p><p>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...</p></blockquote><p></p>
[QUOTE="MacInWin, post: 1764660"] 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... [/QUOTE]
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Apple Computing Products:
macOS - Operating System
Networking - Sierra DHCP Issue
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