Android (lack of) support for DHCPv6

Wed Jun 10 09:52:10 UTC 2015

We use DHCPv6 to assign just one IP address to the CPE. This is because
otherwise our routers do not know where to route the /48 that is also
passed along with DHCPv6-PD.

The routers are stupid I know, but it is what we got. So we simply
implemented a variant of static routes for 2001:db8:x::/48 to
2001:db8::x/128. The DHCP server knows to give you matching /48 and /128.

Apart from operational simplicity, we also do not want our routers to keep
track of a million ND cache entries. Our system pushes that down to the
CPE. In the network we only have one ND cache entry per customer.

The Android tethering guy seems to think that tethering should be a bridge.
But it should of course be routed. The phone in tethering mode should be
getting exactly what we do - one /128 on the uplink interface and a ton of
address space it can use internally and sub delegate to tethering clients.
What exactly is the argument against supporting a sane environment like
that?

As a side note, NAT is not the only solution if someone should try to block
tethering. I would propose a VPN tunnel. You can then have as much address
space you want from the VPN. This is extra easy if you are not locked into
the belief that tethering should be a bridge instead of routed.

Regards,

Baldur