Wi-Fi IPv6 – some windows clients cannot get IPv6 address with SLAAC

[jacardi13]

We’re adding IPv6 connectivity on our existing Wi-Fi network (dual-stack with IPv4) but we got problems with some Windows client. We decide to implement SLAAC because Android clients are not able to get IPv6 address with a stateful solution with DHCPv6.

We are currently in the pilot process. Overall it works well with most of clients (Android, Apple, Linux, Windows,…)

But as already mentioned for some Windows clients we are facing issues when getting an IPv6 address with SLAAC.

There seems to be a problem when the client send its Router Solicitation message as we never receive a Router Advertisement in response.

By capturing the traffic on the client we see the RS message. Then we make some debug on the AP on which the client is associated but there we never see the RS message coming..

Is there a known bug with Windows or Cisco ?

Our Wi-Fi infrastructure use a Cisco Catalyst 9800-40 Controller (release 17.3.3) with a mix of various models of Access Points (AP3700, AP3800, AP Catalyst 9120).

Here are the specifications of the Windows Client used during our tests :

Windows 10 Pro, Version 21H1 (OS Build 19043.1083)

Wireless network card
Intel (R) Wi-Fi 6 AX201 160MHz
Driver Date : 27/05/2021
Driver Version : 22.60.0.6

[patoberli]

I don't really know the Cat9800, but on the previous WLC you had nothing to configure for it to start working. Although it can take 60 seconds or so until the client gets an IPv6 address, at least in my environment. This is assuming your SLAAC router is not the C9800.

In very specific situations you had to enable Multicast support though, not sure if that is needed for SLAAC.

Here is the manual for the C9800: https://www.cisco.com/c/en/us/td/docs/wireless/controller/9800/17-3/config-guide/b_wl_17_3_cg/m_ipv6_client_add_learn_9800.html

[KiPe]

There seems to be a general problem on Windows10 with Intel WiFi NIC, see here:

https://community.intel.com/t5/Wireless/AX201-Stateless-Autoconfiguration-IPv6-not-working-reliably/td-p/1364020

Neither Intel nor MS seem to be willing to fix it on Windows 10. The IPv6 MCAST group needed for SLAAC (RS/RA) is not properly received under specific circumstances.

That said, only few people seem to notice as almost all setups these days are dual stack and so the fallout created by this bug is difficult to map to the root cause. Probably the root cause for a lot of "disable IPv6" kind of advises in public forums ...

Anyone from Cisco having a grip on Intel or MS? ;-]