topic Re: "IP Address Theft" Dual Band WiFi Speed Boost in Wireless

"IP Address Theft" Dual Band WiFi Speed Boost

Amore — Thu, 17 Jul 2025 12:51:08 GMT

Subject: "IP Address Theft" Dual Band WiFi Speed Boost

I encountered a recurring issue in enterprise Wi-Fi setups involving Xiaomi devices. When the Dual Band WiFi Speed Boost feature is enabled, the device connects using both 2.4 GHz and 5 GHz radios, triggering multiple DHCP requests. This leads to IP conflicts, DHCP NAKs, and ARP probes—ultimately causing "IP Address Theft" triggered by WIPS and client constant disconnection.

Disabling the feature resolves the issue. I took me a few weeks to get the logs and analysis.

For full technical details and log analysis, check:
https://itnet.lu/dual_band_dhcp/

Re: "IP Address Theft" Dual Band WiFi Speed Boost

MHM Cisco World — Thu, 17 Jul 2025 12:59:04 GMT

You want solution?

MHM

Re: "IP Address Theft" Dual Band WiFi Speed Boost

Amore — Thu, 17 Jul 2025 13:05:26 GMT

Hi,

The solution is already included, please check the link https://itnet.lu/dual_band_dhcp/. Case was open with Cisco but the TAC was not able to detect the issue.

This post is intended to help others avoid spending unnecessary time and resources on this issue.

Solution summary:

After extensive testing, the culprit was identified: Xiaomi’s Dual Band WiFi Speed Boost. When enabled, this feature:

Connects to the SSID using one radio (e.g., 5 GHz).
Obtains a DHCP lease.
Then connects again using the second radio (e.g., 2.4 GHz), triggering a new DHCP request.

The DHCP server interprets this as a conflict, issues a NAK, and the device sends ARP probes for the invalid IP.

Re: "IP Address Theft" Dual Band WiFi Speed Boost

Rich R — Sat, 19 Jul 2025 21:56:51 GMT

@Amore you don't mention, and neither does the article: does the device use the same MAC address on both bands (in other words trying to get 2 different IP addresses for the same MAC)?
If so then it seems like a pretty stupid feature in my opinion!

WiFi 7 (802.11be) addresses this requirement in a standardised way with MLO.

Re: "IP Address Theft" Dual Band WiFi Speed Boost

Amore — Wed, 06 Aug 2025 08:32:02 GMT

Hi Rich,

I double-checked the capture, and yes — the same MAC address appears when connecting via both 5 GHz and 2.4 GHz bands, as shown in the log with the second DHCP request:

D/DhcpClient(8269): Received packet: 48:7e:25:b1:92:f1 NAK

This matches the MAC address seen on the 5 GHz connection.

The APs model only support 802.11ac Wave 2. This isn't 802.11BE; it's just a variation of dual-band support implemented by certain client vendors.

The challenge with BYOD devices is that you can't manage this feature directly, and you have no visibility into the user's configuration to diagnose the issue. All you get is the usual vague complaint: “The Wi-Fi isn’t working.” 🙂

Xiaomi support basic answer was reset your phone .....

Re: "IP Address Theft" Dual Band WiFi Speed Boost

Rich R — Tue, 19 Aug 2025 10:06:55 GMT

Hmmm interesting - could be server-specific behaviour or would have to see exactly what is in those DHCP requests to understand why it's causing a NAK. My instinct is that most servers would simply treat that as a renew when the MAC address is the same.