Point-to-point using GRE over IPv6 -> not possible with a single /128 address on the server?

[Andreas Nilsson]

On Tue, Feb 19, 2019 at 1:38 PM Peter G. <freebsd at disroot.org> wrote:

> On 15/02/2019 17:49, Peter G. wrote:
> > Now the GRE tunnel
> >
> >> ifconfig gre6 create
> >> ifconfig gre6 inet6 fc01:e::100 fc:02:e::200 tunnelfib 6
> > #ifconfig: ioctl (SIOCAIFADDR): File exists
> >
> > Why is this not possible? Isn't the logic behind it the same as with
> > IPv4? If not, why not?
> >
> > Does this mean it is not possible to have a point-to-point using IPv6 on
> > a machine with only a single /128 address?
>
> Is this a stupid question, or something of the sort? Because I truly
> don't understand why this wouldn't work. Thanks.
>
> PG
>
>
I have not used gre with ipv6, so I cannot really be of any help. However
for ipv4 you specify a netmask while setting up the interface, whereas you
do not while setting up the ipv6. I also notice that you list fc02:e::200
for "other end" but in the commands you have fc:02:e::200 which I guess is
just typo. Does

ifconfig gre6 inet6 fc01:e::100 fc:02:e::200 prefixlen 128 tunnelfib 6

work? Or the whole thing

ifconfig gre6 inet6 fc01:e::100 fc02:e::200 tunnel fc01:e::100 fc02:e::200
prefixlen 128 tunnelfib 6

Best regards
Andreas