OpenStack Networking (Neutron)
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Layer 3 Networking in Neutron - via Layer 3 agent & OpenVSwitch

This page discusses the usage of Neutron with Layer 3 functionality enabled.

Neutron logical network setup

vagrant@bionic64:~/devstack$ openstack network list
+--------------------------------------+---------+----------------------------------------------------------------------------+
| ID                                   | Name    | Subnets                                                                    |
+--------------------------------------+---------+----------------------------------------------------------------------------+
| 6ece2847-971b-487a-9c7b-184651ebbc82 | public  | 0d9c4261-4046-462f-9d92-64fb89bc3ae6, 9e90b059-da97-45b8-8cb8-f9370217e181 |
| 713bae25-8276-4e0a-a453-e59a1d65425a | private | 6fa3bab9-103e-45d5-872c-91f21b52ceda, c5c9f5c2-145d-46d2-a513-cf675530eaed |
+--------------------------------------+---------+----------------------------------------------------------------------------+

vagrant@bionic64:~/devstack$ openstack subnet list
+--------------------------------------+---------------------+--------------------------------------+--------------------+
| ID                                   | Name                | Network                              | Subnet             |
+--------------------------------------+---------------------+--------------------------------------+--------------------+
| 0d9c4261-4046-462f-9d92-64fb89bc3ae6 | public-subnet       | 6ece2847-971b-487a-9c7b-184651ebbc82 | 172.24.4.0/24      |
| 6fa3bab9-103e-45d5-872c-91f21b52ceda | ipv6-private-subnet | 713bae25-8276-4e0a-a453-e59a1d65425a | 2001:db8:8000::/64 |
| 9e90b059-da97-45b8-8cb8-f9370217e181 | ipv6-public-subnet  | 6ece2847-971b-487a-9c7b-184651ebbc82 | 2001:db8::/64      |
| c5c9f5c2-145d-46d2-a513-cf675530eaed | private-subnet      | 713bae25-8276-4e0a-a453-e59a1d65425a | 10.0.0.0/24        |
+--------------------------------------+---------------------+--------------------------------------+--------------------+

vagrant@bionic64:~/devstack$ openstack port list
+--------------------------------------+------+-------------------+----------------------------------------------------------------------------------------------------+--------+
| ID                                   | Name | MAC Address       | Fixed IP Addresses                                                                                 | Status |
+--------------------------------------+------+-------------------+----------------------------------------------------------------------------------------------------+--------+
| 420abb60-2a5a-4e80-90a3-3ff47742dc53 |      | fa:16:3e:2d:5c:4e | ip_address='172.24.4.7', subnet_id='0d9c4261-4046-462f-9d92-64fb89bc3ae6'                          | ACTIVE |
|                                      |      |                   | ip_address='2001:db8::1', subnet_id='9e90b059-da97-45b8-8cb8-f9370217e181'                         |        |
| b42d789d-c9ed-48a1-8822-839c4599301e |      | fa:16:3e:0a:ff:24 | ip_address='10.0.0.1', subnet_id='c5c9f5c2-145d-46d2-a513-cf675530eaed'                            | ACTIVE |
| cfff6574-091c-4d16-a54b-5b7f3eab89ce |      | fa:16:3e:a0:a3:9e | ip_address='10.0.0.2', subnet_id='c5c9f5c2-145d-46d2-a513-cf675530eaed'                            | ACTIVE |
|                                      |      |                   | ip_address='2001:db8:8000:0:f816:3eff:fea0:a39e', subnet_id='6fa3bab9-103e-45d5-872c-91f21b52ceda' |        |
| e3b7fede-277e-4c72-b66c-418a582b61ca |      | fa:16:3e:13:dd:42 | ip_address='2001:db8:8000::1', subnet_id='6fa3bab9-103e-45d5-872c-91f21b52ceda'                    | ACTIVE |
+--------------------------------------+------+-------------------+----------------------------------------------------------------------------------------------------+--------+


vagrant@bionic64:~/devstack$ openstack subnet show c5c9f5c2-145d-46d2-a513-cf675530eaed
+-------------------+--------------------------------------+
| Field             | Value                                |
+-------------------+--------------------------------------+
| allocation_pools  | 10.0.0.2-10.0.0.254                  |
| cidr              | 10.0.0.0/24                          |
| created_at        | 2016-11-08T21:55:22Z                 |
| description       |                                      |
| dns_nameservers   |                                      |
| enable_dhcp       | True                                 |
| gateway_ip        | 10.0.0.1                             |
| host_routes       |                                      |
| id                | c5c9f5c2-145d-46d2-a513-cf675530eaed |
| ip_version        | 4                                    |
| ipv6_address_mode | None                                 |
| ipv6_ra_mode      | None                                 |
| name              | private-subnet                       |
| network_id        | 713bae25-8276-4e0a-a453-e59a1d65425a |
| project_id        | 35e3820f7490493ca9e3a5e685393298     |
| revision_number   | 2                                    |
| service_types     |                                      |
| subnetpool_id     | b1f81d96-d51d-41f3-96b5-a0da16ad7f0d |
| updated_at        | 2016-11-08T21:55:22Z                 |
+-------------------+--------------------------------------+

Neutron logical router setup

vagrant@bionic64:~/devstack$ openstack router list
+--------------------------------------+---------+--------+-------+-------------+-------+----------------------------------+
| ID                                   | Name    | Status | State | Distributed | HA    | Project                          |
+--------------------------------------+---------+--------+-------+-------------+-------+----------------------------------+
| 82fa9a47-246e-4da8-a864-53ea8daaed42 | router1 | ACTIVE | UP    | False       | False | 35e3820f7490493ca9e3a5e685393298 |
+--------------------------------------+---------+--------+-------+-------------+-------+----------------------------------+
vagrant@bionic64:~/devstack$ openstack router show router1
+-------------------------+------------------------------------------------------------------------------------------------------------------------------------------------------+
| Field                   | Value                                                                                                                                                |
+-------------------------+------------------------------------------------------------------------------------------------------------------------------------------------------+
| admin_state_up          | UP                                                                                                                                                   |
| availability_zone_hints |                                                                                                                                                      |
| availability_zones      | nova                                                                                                                                                 |
| created_at              | 2016-11-08T21:55:30Z                                                                                                                                 |
| description             |                                                                                                                                                      |
| distributed             | False                                                                                                                                                |
| external_gateway_info   | {"network_id": "6ece2847-971b-487a-9c7b-184651ebbc82", "enable_snat": true, "external_fixed_ips": [{"subnet_id": "0d9c4261-4046-462f-                |
|                         | 9d92-64fb89bc3ae6", "ip_address": "172.24.4.7"}, {"subnet_id": "9e90b059-da97-45b8-8cb8-f9370217e181", "ip_address": "2001:db8::1"}]}                |
| flavor_id               | None                                                                                                                                                 |
| ha                      | False                                                                                                                                                |
| id                      | 82fa9a47-246e-4da8-a864-53ea8daaed42                                                                                                                 |
| name                    | router1                                                                                                                                              |
| project_id              | 35e3820f7490493ca9e3a5e685393298                                                                                                                     |
| revision_number         | 8                                                                                                                                                    |
| routes                  |                                                                                                                                                      |
| status                  | ACTIVE                                                                                                                                               |
| updated_at              | 2016-11-08T21:55:51Z                                                                                                                                 |
+-------------------------+------------------------------------------------------------------------------------------------------------------------------------------------------+
vagrant@bionic64:~/devstack$ openstack port list --router router1
+--------------------------------------+------+-------------------+---------------------------------------------------------------------------------+--------+
| ID                                   | Name | MAC Address       | Fixed IP Addresses                                                              | Status |
+--------------------------------------+------+-------------------+---------------------------------------------------------------------------------+--------+
| 420abb60-2a5a-4e80-90a3-3ff47742dc53 |      | fa:16:3e:2d:5c:4e | ip_address='172.24.4.7', subnet_id='0d9c4261-4046-462f-9d92-64fb89bc3ae6'       | ACTIVE |
|                                      |      |                   | ip_address='2001:db8::1', subnet_id='9e90b059-da97-45b8-8cb8-f9370217e181'      |        |
| b42d789d-c9ed-48a1-8822-839c4599301e |      | fa:16:3e:0a:ff:24 | ip_address='10.0.0.1', subnet_id='c5c9f5c2-145d-46d2-a513-cf675530eaed'         | ACTIVE |
| e3b7fede-277e-4c72-b66c-418a582b61ca |      | fa:16:3e:13:dd:42 | ip_address='2001:db8:8000::1', subnet_id='6fa3bab9-103e-45d5-872c-91f21b52ceda' | ACTIVE |
+--------------------------------------+------+-------------------+---------------------------------------------------------------------------------+--------+

See the Networking Guide for more detail on the creation of networks, subnets, and routers.

Neutron Routers are realized in OpenVSwitch

image

"router1" in the Neutron logical network is realized through a port ("qr-0ba8700e-da") in OpenVSwitch - attached to "br-int":

vagrant@bionic64:~/devstack$ sudo ovs-vsctl show
b9b27fc3-5057-47e7-ba64-0b6afe70a398
    Bridge br-int
        Port "qr-0ba8700e-da"
            tag: 1
            Interface "qr-0ba8700e-da"
                type: internal
        Port br-int
            Interface br-int
                type: internal
        Port int-br-ex
            Interface int-br-ex
        Port "tapbb60d1bb-0c"
            tag: 1
            Interface "tapbb60d1bb-0c"
                type: internal
        Port "qvob2044570-ad"
            tag: 1
            Interface "qvob2044570-ad"
        Port "int-br-eth1"
            Interface "int-br-eth1"
    Bridge "br-eth1"
        Port "phy-br-eth1"
            Interface "phy-br-eth1"
        Port "br-eth1"
            Interface "br-eth1"
                type: internal
    Bridge br-ex
        Port phy-br-ex
            Interface phy-br-ex
        Port "qg-0143bce1-08"
            Interface "qg-0143bce1-08"
                type: internal
        Port br-ex
            Interface br-ex
                type: internal
    ovs_version: "1.4.0+build0"


vagrant@bionic64:~/devstack$ brctl show
bridge name bridge id       STP enabled interfaces
br-eth1     0000.e2e7fc5ccb4d   no
br-ex       0000.82ee46beaf4d   no      phy-br-ex
                                                        qg-39efb3f9-f0
                                                        qg-77e0666b-cd
br-int      0000.5e46cb509849   no      int-br-ex
                                                        qr-54c9cd83-43
                                                        qvo199abeb2-63
                                                        qvo1abbbb60-b8
                                                        tap74b45335-cc
qbr199abeb2-63      8000.ba06e5f8675c   no      qvb199abeb2-63
                                                        tap199abeb2-63
qbr1abbbb60-b8      8000.46a87ed4fb66   no      qvb1abbbb60-b8
                                                        tap1abbbb60-b8
virbr0      8000.000000000000   yes

Finding the router in ip/ipconfig

The neutron-l3-agent uses the Linux IP stack and iptables to perform L3 forwarding and NAT. In order to support multiple routers with potentially overlapping IP addresses, neutron-l3-agent defaults to using Linux network namespaces to provide isolated forwarding contexts. As a result, the IP addresses of routers will not be visible simply by running "ip addr list" or "ifconfig" on the node. Similarly, you will not be able to directly ping fixed IPs.

To do either of these things, you must run the command within a particular router's network namespace. The namespace will have the name "qrouter-<UUID of the router>.

image

For example:

vagrant@bionic64:~$ openstack router list
+--------------------------------------+---------+-------------------------------------------------------------------------+
| ID                                   | Name    | Status | State | Distributed | HA    | Project                          |
+--------------------------------------+---------+-------------------------------------------------------------------------+
| ad948c6e-afb6-422a-9a7b-0fc44cbb3910 | router1 | Active | UP    | True        | False | 35e3820f7490493ca9e3a5e685393298 |
+--------------------------------------+---------+-------------------------------------------------------------------------+
vagrant@bionic64:~/devstack$ sudo ip netns exec qrouter-ad948c6e-afb6-422a-9a7b-0fc44cbb3910 ip addr list
18: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
19: qr-54c9cd83-43: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN
    link/ether fa:16:3e:dd:c1:8f brd ff:ff:ff:ff:ff:ff
    inet 10.0.0.1/24 brd 10.0.0.255 scope global qr-54c9cd83-43
    inet6 fe80::f816:3eff:fedd:c18f/64 scope link
       valid_lft forever preferred_lft forever
20: qg-77e0666b-cd: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN
    link/ether fa:16:3e:1f:d3:ec brd ff:ff:ff:ff:ff:ff
    inet 192.168.27.130/28 brd 192.168.27.143 scope global qg-77e0666b-cd
    inet6 fe80::f816:3eff:fe1f:d3ec/64 scope link
       valid_lft forever preferred_lft forever

Provider Networking

Neutron can also be configured to create provider networks.

L3 agent extensions

See l3_agent_extensions.

Further Reading