Services / Router Advertisement - DHCPv6 server - strange behavior

[eagle61]

I noticed a strange behavior on Android devices in a local network segment used for IoT-Devices only of my pfsense.

The Router Advertisement Mode for the IoT-Segment are set to Managed. Netgate Docs writes about this mode: "The firewall will send out RA packets and addresses will only be assigned to clients using DHCPv6" and that what i want. All devices shall get either only a IPv4-Adress and a fixed IPv6Adress from activated KEA DHCPv6-Server. So far that works well.

But just because of curiosity and testing purposes i did add an older WIFI-Access Point to this segment and noticed strange behavior of my Android devices if using this WIFI-Access Point.
My phone and my tablet, one using Android 13, the other Android 12. got in this segment also not link local IPv6-Adresses (not starting with fe80 but wth 2a01). That's strange, since, by all i did read so far, Android does not come with any DHCPv6-Client and can not get IPv6-Adresses from any DHCPv6-Server, but only by SLAAC.

So i am curious why the Android Devices gets IPv6-Adresses, if "Managed-Mode" means by definition of Netgate Docs, SLAAC is disabled then and only DHCPv6 shall work and Android can't use DHCPv6-Server for that purpose!?

Oh and the DHCPv6-Server Logs does not show any request for a Lease for this two Android Devices. So even if Netgate Docs writes the opposite, SLAAC seems to be still active even if Router Advertisements are set to Managed.

[Gertjan]

Would like to have the situation clarified also.
More precise : why "Android" doesn't want to use DHCP6 ? What do they have against it ? Is DHCP6 payware for them ? Royalties ?

@eagle61 said in Services / Router Advertisement - IDHCPv6 server - strange behavior:

So i am curious why the Android Devices gets IPv6-Adresses

If your "2a01" is part of your prefix, I can't imaginable that the android device "just auto assigns" an IPv6 'GUA'.

Btw : your are using KEA. For real testing, try also the good old messy "ISC" DHCP6.

[eagle61]

@Gertjan said in Services / Router Advertisement - IDHCPv6 server - strange behavior:

Would like to have the situation clarified also.
More precise : why "Android" doesn't want to use DHCP6 ? What do they have against it ? Is DHCP6 payware for them ? Royalties ?

There is no DHCPv6-Client part of Android OS. I have no idea why not. But with no DHCPv6-Client its impossible to request IPv-6-Adress on any DHCPv6-Server.

Btw : your are using KEA. For real testing, try also the good old messy "ISC" DHCP6.

"ISC" DHCPv6 and also -v4 is deprecated, does not get updates anymore.
KEA is therefore its replacement.

And since there is no rquents of the Android device in the KEA-Log, the Android does not use DHCPv6. So this quenstion cant not be answered by using another DHCPv6-Server but is why is SLAAC still active if Router Advisements shall set SLAAC inactive.

And since i just switched my Firewall 6 weeks ago from IPFire to pfsense, i am still very aware how Android behaves if no SLAAC is present. IPFire did not support any IPv6 at all. That's why i now use pfsense instead.

WIth no IPv6-Support, means no SLAAC in the network, Android creates only link local IPv6-Adress, starting with fe80::

Android never creates any other then link local IPv6-Adress without SLAAC in the network.

[Gertjan]

@eagle61 said in Services / Router Advertisement - IDHCPv6 server - strange behavior:

"ISC" DHCPv6 and also -v4 is deprecated, does not get updates anymore.

Yeah, I know, since 2022 or so. For some reason this became suddenly 'an issue', no no security issues have been found yet.
If so, after all, it would have been said here.

I could find was :

ISC DHCP is very mature code

So, I feel safe ^^ as I trust what the authors say.

However, it is time to start thinking about a migration plan to a more modern system that is actively maintained

As I - I'm just another pfSense user - 'need' Static MAC leases and some DHCP options, kea is still on my 'I think about it' list.

I'll adopt Kea as soon as Netgate has adopted it ^^

[eagle61]

@Gertjan said in Services / Router Advertisement - DHCPv6 server - strange behavior:

I'll adopt Kea as soon as Netgate has adopted it ^^

That's already done. View attachment.

[Bob.Dig]

@eagle61 said in Services / Router Advertisement - DHCPv6 server - strange behavior:

But just because of curiosity and testing purposes i did add an older WIFI-Access Point to this segment

Maybe it is the reason. Because I just tested both, ISC and KEA (without rebooting though) and none of them showed this behavior for me. My "AP" is using VLANs from pfSense.

[JKnott]

@eagle61

Thanks to some genius at Google, Android does not support DHCPv6.

[eagle61]

@JKnott said in Services / Router Advertisement - DHCPv6 server - strange behavior:

Thanks to some genius at Google, Android does not support DHCPv6

Same genius at Google for its Chrome OS ;-)
Does also not fully support RFC 3315

See: https://en.wikipedia.org/wiki/Comparison_of_IPv6_support_in_operating_systems