Wrong prefix length is advertised

Juergen Bachsteffel juebac at web.de
Tue Mar 29 16:46:24 UTC 2016


Simon Hobson <dhcp1 at thehobsons.co.uk> wrote:

Thank you for yourexplanations. Yes, that helped a bit!

>What do "ip -f inet6 route" and "ip -f inet6 neigh" show ?

ip -f inet route:
fda0:65da:e55a:1::200 dev enp0s25  proto kernel  metric 256
fe80::/64 dev enp0s25  proto kernel  metric 256

ip -f inet neigh:
fe80::224:7eff:fedf:b4b3 dev enp0s25 lladdr 00:24:7e:df:b4:b3 router STALE
fda0:65da:e55a:1::3 dev enp0s25 lladdr 00:24:7e:df:b4:b3 router STALE

(please read further)

Sten Carlsen <stenc at s-carlsen.dk> wrote:

>Just to point out that while in IP4 the DHCP gives all info needed, in
>IP6 both DHCP and RADV are needed to have the full picture.

Yes, I know that for the default gateway. There is no option
for the default gateway in DHCPv6. It is advertised through radvd and
normally is the link-local-address from a router.

radvd.conf is:
interface eth0
AdvSendAdvert on;
AdvDefaultLifetime 0;
prefix fda0:65da:e55a:0001::/64

Both radvd and dhcpd6 are a running.

On my Linux-Client with Network-Manager I have two options for IPv6.
"Automatic" and "Automatic, DHCP only".

With 'Automatic' the client gets a IP-address from radvd and there is an
entry when I type: ip -f inet6 route

fda0:65da:e55a:1::/64 dev enp0s25  proto kernel  metric 256  expires

With 'Automatic, DHCP only' the client gets an IP-address from the
DHCP-Server and the entry is missing! (See the first output of ip -6 route).

When I understand your explanations right this could be the reason,
why it isn't working. The client needs an route entry to know, who his
neighbors are, right?

And, I have to find out why the entry is missing.


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