Red Hat Bugzilla – Bug 612445
NetworkManager does not support DHCPv6-only configurations
Last modified: 2010-11-10 14:31:40 EST
Description of problem:
I tried to configure anaconda to use dhcp for ipv6 configuration, however it doesn't even send dhcpv6 request.
I tried ipv6=dhcp on command line as well as proper choice in configuration dialog, nothing was working.
Version-Release number of selected component (if applicable):
NetworkManager plugin ifcfg-rh doesn't support dhcpv6 yet (DHCPV6C ifcfg option).
Even more, neighbor discovery is used instead of dhcp if available.
Note that DHCPv6 is *not* a full IPv6 configuration method since DHCPv6 cannot return the gateway to use to access external networks. You need a combination of router advertisements *and* DHCPv6 (which is used when the router advertisement sets the "otherconf" or "managed" bits).
There was support for DHCPv6-only, but since DHCPv6 doesn't return a gateway (and the DHCPv6 server is not necessarily the gateway) DHCPv6-only support was removed from NM in commit a729d2f649fefc77fcff7ad250c5c403a4dd59b7
Ok, based on discussion I'll revert the revert and we'll get back DHCPv6-only functionality.
Just for a clarification, I reported anaconda (actually NM on backend) does not even send dhcpv6 request even if explicitly requested in configuration dialog, that's the issue in this report. This doesn't necessarily require dhcpv6-only configuration, just dhcpv6 should be used when requested.
It does require DHCPv6-only functionality, because when DHCPv6 is requested, you're asking to *not* use autoconf, but instead to use only DHCPv6.
Normal IPv6 networks would have router advertisements enabled with the "Managed" bit set, at which point NetworkManager will then automatically start DHCPv6 and use the returned information for configuration.
What you're asking the installer/NM to do here is to ignore IPv6 autoconfiguration and manually do a DHCPv6 request, presumably because your network does not have router advertisements enabled. Which is odd (and not really how IPv6 is supposed to work) but is apparently a configuration that people require.
(In reply to comment #7)
> Normal IPv6 networks would have router advertisements enabled with the
> "Managed" bit set...
This is stateless configuration.
> What you're asking the installer/NM to do here is to ignore IPv6
> autoconfiguration and manually do a DHCPv6 request
I am asking here for stateful DHCPv6 configuration. This is what I assume if I choose DHCPv6 in network configuration dialog of installer. IP address (as well as other options) should be assigned by DHCP server.
Additionally, I assume working network configuration in any case (correct router set for example).
Just to be clear, maybe the options in anaconda are wrong (or maybe my understanding is wrong), I can't decide.
Anaconda provides these 2 automatic configuration options:
* Automatic neighbor discovery
- With this option I assume autoconfiguration including stateless DHCPv6
* Dynamic IP configuration (DHCPv6)
- Here I assume complete stateful DHCPv6 configuration, doesn't matter
if 'M' bit in router advertisement is set or not.
(In reply to comment #9)
> Just to be clear, maybe the options in anaconda are wrong (or maybe my
> understanding is wrong), I can't decide.
> Anaconda provides these 2 automatic configuration options:
> * Automatic neighbor discovery
> - With this option I assume autoconfiguration including stateless DHCPv6
> if available.
> * Dynamic IP configuration (DHCPv6)
> - Here I assume complete stateful DHCPv6 configuration, doesn't matter
> if 'M' bit in router advertisement is set or not.
That's probably correct, but "Automatic" will *also* do stateful DHCPv6 if the router sets the 'M' bit. I'd assume the DHCPv6 option there just ignores router advertisements completely.
moving to verified as approved by QE member
Red Hat Enterprise Linux 6.0 is now available and should resolve
the problem described in this bug report. This report is therefore being closed
with a resolution of CURRENTRELEASE. You may reopen this bug report if the
solution does not work for you.