Deploying IPv6-only tenants with OpenStack

In this post, I’ll discuss the deployment of IPv6-only Neutron networks for tenant use. A few things to note about IPv6-only instances:

IPv6-only works out-of-the-box for basic IP connectivity with OpenStack but you are hosed on the metadata service
Many people deploy dual stack in order to overcome the metadata issue
The metadata service only supports IPv4
An old wish list bug has long expired: https://bugs.launchpad.net/neutron/+bug/1460177
Workarounds:
- Build all/most of what you want inside the image itself
- Use config-drive

I’m going to use a very basic “config-drive” example here to show how important stuff (metadata) can be injected into an IPv6-only instance. If you don’t know much about config-drive, Red Hat has a reasonable write-up on it. There is tons of info on it; just search. Also, I’m working from the topology of previous blog posts such as my last one on provider networks. I won’t be going over the topology and OpenStack setup here.

In this example, I have a file called “user_data.yaml” (no dependency on the actual file name). There is not much in it; I have a FQDN defined and a key. The only thing I am testing here is whether or not the defined FQDN (v6onlyinstance.example.com) appears in the instance at boot. Here is the output:

[root@c7-os-1]# cat user_data.yaml
#cloud-config
fqdn: v6onlyinstance.example.com
users:
  - name: cloud-user
    ssh-authorized-keys:
      - ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC4W4RPlOBiY14iJwW9kd3Chys5bUBjy2VKJkFa5az8JHcVvOh3LO5BHdhc6WryT+blmx9LKGyVSc0rfzSEAfQ91dXJCHuhl5BNk9pLibs3oe8s/1r/vjtxQopKIIGN3PYuisvpZVLeP1kRhddIdLvuZcQm82L4VPUAOzLqbFdhsu/Y2lU5WyiTiI5VNJwwbzzc67BFHz2ov2bdBgCfFWyUQMikiyIrAv5hVcqADv7XAqY4P5sJaOaHAcNcCfMtY8RbtEMSIyw8fey1erY4ZiknTAn/eU52mc18l9xR4CwI9wYqYdpVyiNULRWH9opK30dqhhthgElzCax+WqmxMXGP [email protected]

Now, I boot an instance, enable “config-drive” and point to the “user_data.yaml” file. The instance is set to use a Neutron network that I previously added that has an IPv6 prefix setup (no IPv4):

nova boot --flavor m1.small --image rh7-stateless --key-name new-aio-key --security-groups default --nic net-name=external-net rhv6-only-drive --config-drive true --user-data user_data.yaml

Notice that in the “nova list” output below, the name of the instance is “rhv6-only-drive” (based on me naming it that in the “nova boot” command):

[root@c7-os-1 ~]# nova list
+--------------------------------------+-----------------+--------+------------+-------------+---------------------------------------------------
| ID                                   | Name            | Status | Task State | Power State | Networks                                          
+--------------------------------------+-----------------+--------+------------+-------------+---------------------------------------------------
| 2244a346-a34b-4ab6-905f-71dc207a92e6 | rhv6-only-drive | ACTIVE | -          | Running     | external-net=2001:db8:cafe:16:f816:3eff:feec:3c59 
+--------------------------------------+-----------------+--------+------------+-------------+---------------------------------------------------

Login to the instance (notice that I don’t have to mess with no stinking floating IPs or “ip netns” nonsense! No NAT FTW! ? ):

ssh cloud-user@2001:db8:cafe:16:f816:3eff:feec:3c59

Notice that the hostname is what I set in the “FQDN line” of the “user_data.yaml” file and that the instance only has an IPv6 address. Also, the instance has the domain name “example.com” from the FQDN in the yaml file and a “nameserver” is set (the instance is using Stateless DHCPv6):

[cloud-user@v6onlyinstance ~]$ ip a
. . .
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether fa:16:3e:ec:3c:59 brd ff:ff:ff:ff:ff:ff
    inet6 2001:db8:cafe:16:f816:3eff:feec:3c59/64 scope global dynamic
       valid_lft 2591952sec preferred_lft 604752sec
    inet6 fe80::f816:3eff:feec:3c59/64 scope link
       valid_lft forever preferred_lft forever

[cloud-user@v6onlyinstance ~]$ cat /etc/resolv.conf
# Generated by NetworkManager
search openstacklocal. example.com
nameserver 2001:db8:cafe:a::e

[cloud-user@v6onlyinstance ~]$ cat /etc/hostname
v6onlyinstance.example.com

Go ahead, give it a try. You might like IPv6-only. ?

This post first appeared on the Shannon McFarland’s blog. Superuser is always interested in community content, email: [email protected].

By: Remko van Dokkum
// CC BY

Tags: IPv6, tutorial