[GLLUG] Odd deficiency (?) in Gnome Network Manager for IPv6

[John Winters]

I've just noticed something odd.

Given a newly installed Jessie workstation on my home LAN, where native 
IPv6 has been working for some time, if I use the default NIC 
configuration and let the Gnome Network Manager configure the NIC 
(whether hard-wired or WiFi) it picks up the expected global IPv6 
address, but it can't communicate to other machines outside the LAN 
using IPv6.  Communication with local machines over IPv6 works fine.

Simply adding the following lines to /etc/network/interfaces:


   auto eth0
   iface eth0 inet dhcp

   iface eth0 inet6 auto

cures the problem, and the machine then has full IPv6 connectivity.  Of 
course this means that Network Manager isn't touching the interface and 
it's being configured instead by the old-fashioned networking scripts.

I'm presuming this is a routing problem, but I'm not that familiar with 
IPv6 yet - it seems much more complicated than the old two routes (local 
and default gateway) one had with IPv4.

Can anyone offer me any guidance on where to start looking?

Cheers,
John