Re: IPv6 with DHCP -- how is default route set?

On Tue, 2015-10-20 at 11:29 -0400, Eloy Paris wrote:

The company I work for has an IPv6-enabled network that requires
configuration via DHCP. I get assigned a global IPv6 address just
after configuring the NetworkManager entry for my NIC with
DHCP only".

Usually, the default gateway comes via the Router-Advertisements.

I would rather expect that you choose


which will use RA + DHCP6 (if the RouterAdvertisements indicate to use

"Automatic, DHCP only" will not use RA at all.

The problem, however, is that a default route is never installed. I
confused as to who is responsible for setting up the default route,
which should be learned via Neighbor Discovery router advertisement
messages, which I am seeing:

11:22:13.534922 IP6 (class 0xe0, hlim 255, next-header ICMPv6 (58)
payload length: 64) fe80::208:e3ff:feff:fd90 > ff02::1: [icmp6 sum
ok] ICMP6, router advertisement, length 64
      hop limit 64, Flags [managed], pref medium, router lifetime
1800s, reachable time 0s, retrans time 0s
        source link-address option (1), length 8 (1):
          0x0000:  0008 e3ff fd90
        mtu option (5), length 8 (1):  1500
          0x0000:  0000 0000 05dc
        prefix info option (3), length 32 (4): 2001:x:x:x::/64, Flags
[onlink], valid time 0s, pref. time 0s

For this to work, do I need a userspace daemon that processes these
router advertisement messages?

That deamon to do RA in userspace is NetworkManager.

Or can the kernel install the default
route if some tunables like accept_ra are set properly? I notice that
NetworkManager seems to set accept_ra to 0, though, and there is no
to configure the behavior that I can see.

I've searched online left and right but have not been able to find a
conclusive answer on how to properly set up NetworkManager so IPv6
DHCP configuration is usable beyond the local subnet. Pointers would
greatly appreciated.

Running NetworkManager 1.0.4 with Linux kernel 4.2.0 (this is what
with Ubuntu 15.10, which is about to release in the next day or two).

Also make sure that the connection is not never-default (by default it
is never-default=no):

  nmcli connection show $CON_NAME | grep ipv6.never-default

Also note, you can configure the ipv6.gateway property manually too.


Attachment: signature.asc
Description: This is a digitally signed message part

[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]