IPv6 deployment on OpenStack
marc-antoine.godde at viarezo.fr
Tue Mar 8 16:18:05 UTC 2022
Here’s what we’ve done.
We created a network:
Network Type: vlan
Physical Network: vlan
Segmentation ID: 51
We created a subnet:
9d5ca309-1861-4422-bcff-8818f9762a6f <https://openstack.viarezo.fr/project/networks/9d5ca309-1861-4422-bcff-8818f9762a6f/detail>Subnet Pool
IP Allocation Pools
Start xxxx:xxxx:2f1:aaaa::2 - End xxxx:xxxx:2f1:aaaa:ffff:ffff:ffff:ffff
IPv6 Address Configuration Mode
SLAAC: Address discovered from OpenStack Router
DNS Name Servers
We created Ubuntu and Debian instances. According to Horizon, the instance IPv6 is xxxx:xxxx:2f1:aaaa:f816:3eff:fe6d:c41a. Yet, we only have a link local address which is fe80::f816:3eff:fe6d:c41a/64. TCPdump indicates no Router Advertisement. We tried with and without adding a router on the Network in Horizon. ICMPv6 is authorized in INGRESS from ::/0.
We checked on the controllers, the computes and in the Neutron containers, systemctl indicated no instance of RADVD. Maybe we checked incorrectly...
Do you have any suggestions ? I add that we are working with OpenStack Ussuri deployed with OpenStack-ansible.
> Le 8 mars 2022 à 08:59, Slawek Kaplonski <skaplons at redhat.com> a écrit :
> On poniedziałek, 7 marca 2022 10:36:30 CET Marc-Antoine Godde wrote:
>> Thanks for your answer.
>> If I’m correct, we can just use a virtual router with SLAAC since RADVD can deal with RS and emit RA (with support for RFC6106), right ?
> Yes, virtual router created in the Neutron is enough there. It will spawn radvd in the qrouter namespace and will send RA to the Vms.
> Please note that Neutron don't supports privacy extension  so You will need to make sure that it's disabled it on Your vms.
>> More generally, aren’t we suppose to have a virtual router every time, even in DHCPv6 (stateless and statefull), to answer RS ? I have to admit that I’m not very familiar at the moment with the implementations of RFCs in OpenStack.
>> Currently, we prefer the idea of adding IPv6 through SLAAC to have a uniform network. If we do so, we’d like to avoid sending RA from our physical router to limit its load. Yet, we do not any other arguments to support this choice.
>> Do you have any recommendations on what to do in latest versions of OpenStack ? What is usually done ?
> TBH I don't have such experience. That's more question to operators of OpenStack.
>>> Le 7 mars 2022 à 09:12, Slawek Kaplonski <skaplons at redhat.com> a écrit :
>>> On poniedziałek, 7 marca 2022 02:36:24 CET Marc-Antoine Godde wrote:
>>>> We are progressively adding support for IPv6 in my company. We decided to use SLAAC only for laptops, phones, … since DHCPv6 isn’t supported on Android. RDNSS support will also increase. We are now planning our deployment on OpenStack. We already know that we'll rely only on neutron but we are not yet fixed between DHCPv6 and SLAAC ? Do you have any arguments for one these for VMs ?
>>> With SLAAC You need to have Your network connected to the router in Neutron and You can only configure IP address on the VM. With DHCPv6 You can configure other things, like some static-routes, etc.
>>> Neutron supports DHCPv6 in the stateful and stateless variants. With stateless, You are using RA for address configuration and DHCP server for other configation. Please see  for more details.
>>>  https://docs.openstack.org/neutron/latest/admin/config-ipv6.html#address-modes-for-ports
>  https://datatracker.ietf.org/doc/html/rfc4941 <https://datatracker.ietf.org/doc/html/rfc4941>
> Slawek Kaplonski
> Principal Software Engineer
> Red Hat
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