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LPhngHin-7668 avatar image
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LPhngHin-7668 asked ·

A mobile device gets 2 IP address in DHCP server

Hi guys, I created DHCP server on Windows server 2016 (ver 1607 (build 14393.4225). When mobile devices join my network, I see some devices show in address leases take multi IP address with difference Unique ID. What happen with them? Could you please help me resolve this problem? ![72551-dhcp.png][1] [1]: /answers/storage/attachments/72551-dhcp.png

windows-dhcp-dns
dhcp.png (127.6 KiB)
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SunnyQi-MSFT answered ·

Hi,

Thanks for posting in Q&A platform.

Based on my knowledge, the Unique ID in DHCP server means MAC address of the DHCP client. DHCP server assign available IP address based on MAC address of DHCP client. According to the provided screenshot, the DHCP client with same hostname but has different MAC address.

Please help to confirm if these DHCP clients are different mobile devices or the same mobile device.

If they are the same mobile device and if it has several interfaces, every interface will has its own MAC address, DHCP server assign IP addresses according to the different MAC address, the behavior of DHCP server is normal.

If they are different mobile devices, the behavior of DHCP server is normal as well. Although the hostname of these devices are same, the MAC addresses are different, as above working flow, the behavior of DHCP server is normal.

For more details regarding how DHCP works, please refer to the following article:

How DHCP Technology Works

Best Regards,
Sunny


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hi Sunny,

Thank you for the answer.

I want to confirm that, the DHCP client with same hostname are the same mobile device.

Each mobile device (Iphone 11 pro, Samsung S20...) has a physical wifi MAC address only, but when join my network they have mutil Unique ID.

It makes me confused.

Regards,

Hien Le

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Hi Hien,

Thank you very much for your feedback.

May I know what's the exactly MAC address of these mobile devices? If the exactly MAC address listed in these IP leases?

And in mobile device, how many IP addresses obtained?

How about delete these IP leases and reobtain IP from DHCP server? If the issue still existed?

Best Regards,
Sunny


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Hi Sunny,

I think I found the cause of the problem. From Androi 10, MAC randomized funcion of wifi is turn on automatic. That's why one mobile device has mutil MAC.

Regards

73645-mac-randomized-mac.jpg



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