Android and DHCPv6 again

Baldur Norddahl baldur.norddahl at
Sun Oct 4 01:52:05 UTC 2015


I noticed that my Nexus 9 tablet did not have any IPv6 although everything
else in my house is IPv6 enabled. Then I noticed that my Samsung S6 was
also without IPv6. Hmm.

A little work with tcpdump and I got this:

03:27:15.978826 IP6 (hlim 255, next-header ICMPv6 (58) payload length: 120)
fe80::222:7ff:fe49:ffad > ip6-allnodes: [icmp6 sum ok] ICMP6, router
advertisement, length 120
hop limit 0, Flags [*managed*, other stateful], pref medium, router
lifetime 1800s, reachable time 0s, retrans time 0s
 source link-address option (1), length 8 (1): 00:22:07:49:ff:ad
 mtu option (5), length 8 (1):  1500
 prefix info option (3), length 32 (4): 2a00:7660:5c6::/64, Flags [onlink,
*auto*], valid time 7040s, pref. time 1800s
 unknown option (24), length 16 (2):
 0x0000:  3000 0000 1b80 2a00 7660 05c6 0000

So my CPE is actually doing DHCPv6 and some nice people at Google decided
that it will be better for me to be without IPv6 in that case :-(.

But it also has the auto flag, so Android should be able to do SLAAC yes?

My Macbook Pro currently has the following set of addresses:

ether 3c:15:c2:ba:76:d4
inet6 fe80::3e15:c2ff:feba:76d4%en0 prefixlen 64 scopeid 0x4
inet netmask 0xffffff00 broadcast
inet6 2a00:7660:5c6::3e15:c2ff:feba:76d4 prefixlen 64 autoconf
inet6 2a00:7660:5c6::b5a5:5839:ca0f:267e prefixlen 64 autoconf temporary
inet6 2a00:7660:5c6::899 prefixlen 64 dynamic
nd6 options=1<PERFORMNUD>
media: autoselect
status: active

To me it seems that the Macbook has one SLAAC address, one privacy
extension address and one DHCPv6 managed address.

In fact the CPE manufacturer is a little clever here. They gave me an easy
address that I can use to access my computer ("899") while still allowing
SLAAC and privacy extensions. If I want to open ports in my firewall I
could do that to the "899" address.

But why is my Android devices without IPv6 in this setup?



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