Re: IPv6 Prefix Delegation through Network Manager

Thanks Thomas. Going into debug was able to point me in the right
direction. For those stumbling on this like myself, the
"ipv6.method=shared" refers to your *LAN* interface, not your WAN
interface. While this might seem intuitive to some, when I think
"shared" I think of the WAN though that is mostly a holdover from IPv4

In an earlier fit of desperation I had tried setting the LAN interface
to "shared", but at the time ipv6 ICMP was unintentionally blocked by
the firewall which was preventing the negotiation with my ISP from
happening. I eventually figured it out that it was the firewall when I
switched to wide-dhcpv6 using the known working config I had used with
my old router, but I never went back to try setting the LAN interface
to shared.

After switching to debug I was able to see that the errors hinted at
NM trying to find an interface(device) other than my WAN to assign a
range to. The informational level message "no device to obtain a
subnet to share on <interface> from" sort of gives this away but by
itself can appear a bit cryptic, especially if like me you don't fully
understand how ipv6 works.

I think it would really help out if the documentation had a smidgen
more detail, even if it was just a "for example if you are configuring
a router for prefix delegation you would want to set your
LAN/local/whatever interface to shared mode". Maybe it's already
supposed to appear obvious but I definitely missed it, for what it's

Thanks again Thomas and thanks Vladimir; your earlier post was what
made me aware Network Manager began supporting prefix delegation in
the first place.

On Wed, Sep 5, 2018 at 8:11 AM Thomas Haller <thaller redhat com> wrote:

On Tue, 2018-09-04 at 09:29 -0500, dag dg via networkmanager-list

There doesn't seem to be much documentation for Network Manager on
prefix delegation support. Any insight would be appreciated.


it's not much documented, because there isn't much to configure about
ipv6.method=shared. It's supposed to just work -- except when it

Could you provide a full logfile with level=TRACE enabled?

See the hints about logging at


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