Scope:
To enable a dual-stack network in OpenStack Networking simply requires
creating a subnet with the ip_version
field set to 6
, then the
IPv6 attributes (ipv6_ra_mode
and ipv6_address_mode
) set. The
ipv6_ra_mode
and ipv6_address_mode
will be described in detail in
the next section. Finally, the subnets cidr
needs to be provided.
Things not in the scope of this document include:
As of Juno, the OpenStack Networking service (neutron) provides two new attributes to the subnet object, which allows users of the API to configure IPv6 subnets.
There are two IPv6 attributes:
ipv6_ra_mode
ipv6_address_mode
These attributes can be set to the following values:
slaac
dhcpv6-stateful
dhcpv6-stateless
The attributes can also be left unset.
The ipv6_address_mode
attribute is used to control how addressing is
handled by OpenStack. There are a number of different ways that guest
instances can obtain an IPv6 address, and this attribute exposes these
choices to users of the Networking API.
The ipv6_ra_mode
attribute is used to control router
advertisements for a subnet.
The IPv6 Protocol uses Internet Control Message Protocol packets (ICMPv6) as a way to distribute information about networking. ICMPv6 packets with the type flag set to 134 are called “Router Advertisement” packets, which broadcasts information about the router and the route that can be used by guest instances to send network traffic.
The ipv6_ra_mode
is used to specify if the Networking service should
transmit ICMPv6 packets, for a subnet.
ipv6 ra mode | ipv6 address mode | radvd A,M,O | External Router A,M,O | Description |
---|---|---|---|---|
N/S | N/S | Off | Not Defined | Backwards compatibility with pre-Juno IPv6 behavior. |
N/S | slaac | Off | 1,0,0 | Guest instance obtains IPv6 address from non-OpenStack router using SLAAC. |
N/S | dhcpv6-stateful | Off | 0,1,1 | Not currently implemented in the reference implementation. |
N/S | dhcpv6-stateless | Off | 1,0,1 | Not currently implemented in the reference implementation. |
slaac | N/S | 1,0,0 | Off | Not currently implemented in the reference implementation. |
dhcpv6-stateful | N/S | 0,1,1 | Off | Not currently implemented in the reference implementation. |
dhcpv6-stateless | N/S | 1,0,1 | Off | Not currently implemented in the reference implementation. |
slaac | slaac | 1,0,0 | Off | Guest instance obtains IPv6 address from OpenStack managed radvd using SLAAC. |
dhcpv6-stateful | dhcpv6-stateful | 0,1,1 | Off | Guest instance obtains IPv6 address from dnsmasq using DHCPv6 stateful and optional info from dnsmasq using DHCPv6. |
dhcpv6-stateless | dhcpv6-stateless | 1,0,1 | Off | Guest instance obtains IPv6 address from OpenStack managed radvd using SLAAC and optional info from dnsmasq using DHCPv6. |
slaac | dhcpv6-stateful | Invalid combination. | ||
slaac | dhcpv6-stateless | Invalid combination. | ||
dhcpv6-stateful | slaac | Invalid combination. | ||
dhcpv6-stateful | dhcpv6-stateless | Invalid combination. | ||
dhcpv6-stateless | slaac | Invalid combination. | ||
dhcpv6-stateless | dhcpv6-stateful | Invalid combination. |
Both the Linux bridge and the Open vSwitch dataplane modules support forwarding IPv6 packets amongst the guests and router ports. Similar to IPv4, there is no special configuration or setup required to enable the dataplane to properly forward packets from the source to the destination using IPv6. Note that these dataplanes will forward Link-local Address (LLA) packets between hosts on the same network just fine without any participation or setup by OpenStack components after the ports are all connected and MAC addresses learned.
There are four methods for a subnet to get its cidr
in OpenStack:
In the future, different techniques could be used to allocate subnets to projects:
Note
That an external DHCPv6 server in theory could override the full address OpenStack assigns based on the EUI-64 address, but that would not be wise as it would not be consistent through the system.
IPv6 supports three different addressing schemes for address configuration and for providing optional network information.
OpenStack can be setup such that OpenStack Networking directly
provides RA, DHCP
relay and DHCPv6 address and optional information for their networks
or this can be delegated to external routers and services based on the
drivers that are in use. There are two neutron subnet attributes -
ipv6_ra_mode
and ipv6_address_mode
– that determine how IPv6
addressing and network information is provided to project instances:
ipv6_ra_mode
: Determines who sends RA.ipv6_address_mode
: Determines how instances obtain IPv6 address,
default gateway, or optional information.For the above two attributes to be effective, enable_dhcp
of the
subnet object must be set to True.
When using SLAAC, the currently supported combinations for ipv6_ra_mode
and
ipv6_address_mode
are as follows.
ipv6_ra_mode | ipv6_address_mode | Result |
---|---|---|
Not specified. | SLAAC | Addresses are assigned using EUI-64, and an external router will be used for routing. |
SLAAC | SLAAC | Address are assigned using EUI-64, and OpenStack Networking provides routing. |
Setting ipv6_ra_mode
to slaac
will result in OpenStack Networking
routers being configured to send RA packets, when they are created.
This results in the following values set for the address configuration
flags in the RA messages:
New or existing Neutron networks that contain a SLAAC enabled IPv6 subnet will result in all neutron ports attached to the network receiving IPv6 addresses. This is because when RA broadcast messages are sent out on a neutron network, they are received by all IPv6 capable ports on the network, and each port will then configure an IPv6 address based on the information contained in the RA packet. In some cases, an IPv6 SLAAC address will be added to a port, in addition to other IPv4 and IPv6 addresses that the port already has been assigned.
For DHCPv6-stateless, the currently supported combinations are as follows:
ipv6_ra_mode | ipv6_address_mode | Result |
---|---|---|
DHCPv6-stateless | DHCPv6-stateless | Address and optional information using neutron router and DHCP implementation respectively. |
DHCPv6-stateful | DHCPv6-stateful | Addresses and optional information are assigned using DHCPv6. |
Setting DHCPv6-stateless for ipv6_ra_mode
configures the neutron
router with radvd agent to send RAs. The table below captures the
values set for the address configuration flags in the RA packet in
this scenario. Similarly, setting DHCPv6-stateless for
ipv6_address_mode
configures neutron DHCP implementation to provide
the additional network information.
The behavior of the neutron router for IPv6 is different than IPv4 in a few ways.
Internal router ports, that act as default gateway ports for a network, will share a common port for all IPv6 subnets associated with the network. This implies that there will be an IPv6 internal router interface with multiple IPv6 addresses from each of the IPv6 subnets associated with the network and a separate IPv4 internal router interface for the IPv4 subnet. On the other hand, external router ports are allowed to have a dual-stack configuration with both an IPv4 and an IPv6 address assigned to them.
Neutron project networks that are assigned Global Unicast Address (GUA) prefixes and addresses don’t require NAT on the neutron router external gateway port to access the outside world. As a consequence of the lack of NAT the external router port doesn’t require a GUA to send and receive to the external networks. This implies a GUA IPv6 subnet prefix is not necessarily needed for the neutron external network. By default, a IPv6 LLA associated with the external gateway port can be used for routing purposes. To handle this scenario, the implementation of router-gateway-set API in neutron has been modified so that an IPv6 subnet is not required for the external network that is associated with the neutron router. The LLA address of the upstream router can be learned in two ways.
ipv6_gateway
flag can be set
with the external router gateway LLA in the neutron L3 agent configuration
file. This also requires that no subnet is associated with that port.ipv6_gateway
flag is not set.Effectively the ipv6_gateway
flag takes precedence over an RA that
is received from the upstream router. If it is desired to use a GUA
next hop that is accomplished by allocating a subnet to the external
router port and assigning the upstream routers GUA address as the
gateway for the subnet.
Note
That it should be possible for projects to communicate with each other on an isolated network (a network without a router port) using LLA with little to no participation on the part of OpenStack. The authors of this section have not proven that to be true for all scenarios.
Note
When using the neutron L3 agent in a configuration where it is
auto-configuring an IPv6 address via SLAAC, and the agent is
learning its default IPv6 route from the ICMPv6 Router Advertisement,
it may be necessary to set the
net.ipv6.conf.<physical_interface>.accept_ra
sysctl to the
value 2
in order for routing to function correctly.
For a more detailed description, please see the bug.
IPv6 does work when the Distributed Virtual Router functionality is enabled, but all ingress/egress traffic is via the centralized router (hence, not distributed). More work is required to fully enable this functionality.
VPNaaS supports IPv6, but support in Kilo and prior releases will have
some bugs that may limit how it can be used. More thorough and
complete testing and bug fixing is being done as part of the Liberty
release. IPv6-based VPN-as-a-Service is configured similar to the IPv4
configuration. Either or both the peer_address
and the
peer_cidr
can specified as an IPv6 address. The choice of
addressing modes and router modes described above should not impact
support.
TODO
FWaaS allows creation of IPv6 based rules.
At the current time OpenStack Networking does not provide any facility to support any flavor of NAT with IPv6. Unlike IPv4 there is no current embedded support for floating IPs with IPv6. It is assumed that the IPv6 addressing amongst the projects are using GUAs with no overlap across the projects.
OpenStack currently doesn’t support the privacy extensions defined by RFC 4941. The interface identifier and DUID used must be directly derived from the MAC as described in RFC 2373. The compute hosts must not be setup to utilize the privacy extensions when generating their interface identifier.
There is no provisions for an IPv6-based metadata service similar to what is provided for IPv4. In the case of dual stack Guests though it is always possible to use the IPv4 metadata service instead.
Unlike IPv4 the MTU of a given network can be conveyed in the RA messages sent by the router and not in the DHCP messages.
As of the Kilo release, considerable effort has gone in to ensuring the project network can handle dual stack IPv6 and IPv4 transport across the variety of configurations describe above. OpenStack control network can be run in a dual stack configuration and OpenStack API endpoints can be accessed via an IPv6 network. At this time, Open vSwitch (OVS) tunnel types - STT, VXLAN, GRE, support both IPv4 and IPv6 endpoints.
From the Liberty release onwards, OpenStack Networking supports IPv6 prefix delegation. This section describes the configuration and workflow steps necessary to use IPv6 prefix delegation to provide automatic allocation of subnet CIDRs. This allows you as the OpenStack administrator to rely on an external (to the OpenStack Networking service) DHCPv6 server to manage your project network prefixes.
Note
Prefix delegation became available in the Liberty release, it is not available in the Kilo release. HA and DVR routers are not currently supported by this feature.
To enable prefix delegation, edit the /etc/neutron/neutron.conf
file.
If you are running OpenStack Liberty, make the following change:
default_ipv6_subnet_pool = prefix_delegation
Otherwise if you are running OpenStack Mitaka, make this change:
ipv6_pd_enabled = True
Note
If you are not using the default dibbler-based driver for prefix
delegation, then you also need to set the driver in
/etc/neutron/neutron.conf
:
pd_dhcp_driver = <class path to driver>
Drivers other than the default one may require extra configuration, please refer to Extra configuration
This tells OpenStack Networking to use the prefix delegation mechanism for subnet allocation when the user does not provide a CIDR or subnet pool id when creating a subnet.
To use this feature, you need a prefix delegation capable DHCPv6 server that is reachable from your OpenStack Networking node(s). This could be software running on the OpenStack Networking node(s) or elsewhere, or a physical router. For the purposes of this guide we are using the open-source DHCPv6 server, Dibbler. Dibbler is available in many Linux package managers, or from source at https://github.com/tomaszmrugalski/dibbler.
When using the reference implementation of the OpenStack Networking prefix delegation driver, Dibbler must also be installed on your OpenStack Networking node(s) to serve as a DHCPv6 client. Version 1.0.1 or higher is required.
This guide assumes that you are running a Dibbler server on the network node where the external network bridge exists. If you already have a prefix delegation capable DHCPv6 server in place, then you can skip the following section.
After installing Dibbler, edit the /etc/dibbler/server.conf
file:
script "/var/lib/dibbler/pd-server.sh"
iface "br-ex" {
pd-class {
pd-pool 2001:db8:2222::/48
pd-length 64
}
}
The options used in the configuration file above are:
script
Points to a script to be run when a prefix is delegated or
released. This is only needed if you want instances on your
subnets to have external network access. More on this below.iface
The name of the network interface on which to listen for
prefix delegation messages.pd-pool
The larger prefix from which you want your delegated
prefixes to come. The example given is sufficient if you do
not need external network access, otherwise a unique
globally routable prefix is necessary.pd-length
The length that delegated prefixes will be. This must be
64 to work with the current OpenStack Networking reference implementation.To provide external network access to your instances, your Dibbler server also
needs to create new routes for each delegated prefix. This is done using the
script file named in the config file above. Edit the
/var/lib/dibbler/pd-server.sh
file:
if [ "$PREFIX1" != "" ]; then
if [ "$1" == "add" ]; then
sudo ip -6 route add ${PREFIX1}/64 via $REMOTE_ADDR dev $IFACE
fi
if [ "$1" == "delete" ]; then
sudo ip -6 route del ${PREFIX1}/64 via $REMOTE_ADDR dev $IFACE
fi
fi
The variables used in the script file above are:
$PREFIX1
The prefix being added/deleted by the Dibbler server.$1
The operation being performed.$REMOTE_ADDR
The IP address of the requesting Dibbler client.$IFACE
The network interface upon which the request was received.The above is all you need in this scenario, but more information on installing, configuring, and running Dibbler is available in the Dibbler user guide, at http://klub.com.pl/dhcpv6/doc/dibbler-user.pdf.
To start your Dibbler server, run:
# dibbler-server run
Or to run in headless mode:
# dibbler-server start
When using DevStack, it is important to start your server after the
stack.sh
script has finished to ensure that the required network
interfaces have been created.
First, create a network and IPv6 subnet:
$ neutron net-create ipv6-pd
Created a new network:
+-----------------+--------------------------------------+
| Field | Value |
+-----------------+--------------------------------------+
| admin_state_up | True |
| id | 31ef3e85-111f-4772-8172-8e4a404a7476 |
| mtu | 1450 |
| name | ipv6-pd |
| router:external | False |
| shared | False |
| status | ACTIVE |
| subnets | |
| tenant_id | 28b39bcce66e4a648f82e2362b958b60 |
+-----------------+--------------------------------------+
$ neutron subnet-create ipv6-pd --name ipv6-pd-1 --ip_version 6 \
--ipv6_ra_mode slaac --ipv6_address_mode slaac --use_default_subnetpool
Created a new subnet:
+-------------------+--------------------------------------------------+
| Field | Value |
+-------------------+--------------------------------------------------+
| allocation_pools | {"start": "::2", "end": "::ffff:ffff:ffff:fffe"} |
| cidr | ::/64 |
| dns_nameservers | |
| enable_dhcp | True |
| gateway_ip | ::1 |
| host_routes | |
| id | ea139dcd-17a3-4f0a-8cca-dff8b4e03f8a |
| ip_version | 6 |
| ipv6_address_mode | slaac |
| ipv6_ra_mode | slaac |
| name | ipv6-pd-1 |
| network_id | 31ef3e85-111f-4772-8172-8e4a404a7476 |
| subnetpool_id | prefix_delegation |
| tenant_id | 28b39bcce66e4a648f82e2362b958b60 |
+-------------------+--------------------------------------------------+
The subnet is initially created with a temporary CIDR before one can be
assigned by prefix delegation. Any number of subnets with this temporary CIDR
can exist without raising an overlap error. The subnetpool_id is automatically
set to prefix_delegation
.
To trigger the prefix delegation process, create a router interface between this subnet and a router with an active interface on the external network:
$ neutron router-interface-add cb9b7a2c-0ffa-412f-989a-1e6c60e1c02f \
ea139dcd-17a3-4f0a-8cca-dff8b4e03f8a
Added interface a7e4d663-e3fc-4b8f-909f-865c397a930e to router
cb9b7a2c-0ffa-412f-989a-1e6c60e1c02f.
The prefix delegation mechanism then sends a request via the external network to your prefix delegation server, which replies with the delegated prefix. The subnet is then updated with the new prefix, including issuing new IP addresses to all ports:
$ neutron subnet-show ipv6-pd-1
+-------------------+-------------------------------------------------+
| Field | Value |
+-------------------+-------------------------------------------------+
| allocation_pools | {"start": "2001:db8:2222:6977::2", |
| | "end":"2001:db8:2222:6977:ffff:ffff:ffff:fffe"} |
| cidr | 2001:db8:2222:6977::/64 |
| dns_nameservers | |
| enable_dhcp | True |
| gateway_ip | 2001:db8:2222:6977::1 |
| host_routes | |
| id | ea139dcd-17a3-4f0a-8cca-dff8b4e03f8a |
| ip_version | 6 |
| ipv6_address_mode | slaac |
| ipv6_ra_mode | slaac |
| name | ipv6-pd-1 |
| network_id | 31ef3e85-111f-4772-8172-8e4a404a7476 |
| subnetpool_id | prefix_delegation |
| tenant_id | 28b39bcce66e4a648f82e2362b958b60 |
+-------------------+-------------------------------------------------+
If the prefix delegation server is configured to delegate globally routable prefixes and setup routes, then any instance with a port on this subnet should now have external network access.
Deleting the router interface causes the subnet to be reverted to the temporary CIDR, and all ports have their IPs updated. Prefix leases are released and renewed automatically as necessary.
The following link provides a great step by step tutorial on setting up IPv6 with OpenStack: http://www.debug-all.com/?p=52
To enable the driver for the dhcpv6_pd_agent, set pd_dhcp_driver to this in
/etc/neutron/neutron.conf
:
pd_dhcp_driver = neutron_pd_agent
To allow the neutron-pd-agent to communicate with prefix delegation servers,
you must set which network interface to use for external communication. In
DevStack the default for this is br-ex
:
pd_interface = br-ex
Once you have stacked run the command below to start the neutron-pd-agent:
neutron-pd-agent --config-file /etc/neutron/neutron.conf
Except where otherwise noted, this document is licensed under Creative Commons Attribution 3.0 License. See all OpenStack Legal Documents.