Cisco ACI Installation Guide for Red Hat OpenStack Using the OpenStack Platform 16.1 Director

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Cisco ACI Installation Guide for Red Hat OpenStack Using the OpenStack Platform 16.1 Director

Chapter Title

Add an OpenStack External Network

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Updated:
February 17, 2021

Chapter: Add an OpenStack External Network

Add an OpenStack External Network

Add an OpenStack External Network

This section describes how to add an OpenStack external network.


Note
Execute the commands in this procedure sourcing the keystone file for the project where you want to create the network constructs and the instance.

Before you begin

You must have done the following before adding an OpenStack external network:

  • Created a Layer 3 outside connection (L3Out) in Cisco Application Centric Infrastructure (ACI).

    The L3Out can be in the OpenStack-created tenant (dedicated L3out for the OpenStack tenant) or in the Common tenant (Shared L3out across multiple OpenStack tenants). This procedure assumes that a dedicated L3out called l3out1 is configured in the OpenStack tenant.

  • Specified the following in the L3Out:

    • Interfaces and their IP address information.

    • Dynamic routing, if used.

    • An external endpoint group (EPG).

      This procedure uses an external EPG named extEpg.


Note
Do not add any contracts; the plug-in adds them automatically.

Important
If you require Source Network Address Translation (SNAT) or a floating IP (FIP) address, you must define the L3Out in a different VRF from the one created by OpenStack.

Procedure

Step 1

Create the Neutron external network and provide the distinguished name of the L3Out.

Example:

neutron net-create network_name --router:external --apic:distinguished_names type=dict ExternalNetwork=uni/tn-ACI_tenant_name/out-ACI_L3out_name/instP-ACI_externalEPG_name (--apic:nat_type "")

--apic:nat_type "" is optional. Use it only if you do not use NAT for the specific external Neutron network.

The following shows an example of the creation of the external network with NAT enabled:

neutron net-create external-net-dedicated --router:external --apic:distinguished_names
type=dict ExternalNetwork=uni/tn-prj_$demo01/out-l3out1/instP-extEpg
Created a new network:
+--------------------------------------+------------------------------------------------------+
| Field                                | Value                                                |
+--------------------------------------+------------------------------------------------------+
| admin_state_up                       | True                                                 |
| apic:bgp_asn                         | 0                                                    |
| apic:bgp_enable                      | False                                                |
| apic:bgp_type                        | default_export                                       |
| apic:distinguished_names             | {"EndpointGroup": 
"uni/tn-prj_cdeda9c674a94394a09e86a2fea498c2/ap-OpenStack/epg-EXT-l3out1", 
"ExternalNetwork": "uni/tn-prj_cdeda9c674a94394a09e86a2fea498c2/out-l3out1/instP-extEpg", 
"VRF": "uni/tn-prj_cdeda9c674a94394a09e86a2fea498c2/ctx-externalVRF", "BridgeDomain": 
"uni/tn-prj_cdeda9c674a94394a09e86a2fea498c2/BD-EXT-l3out1"}                                  |
| apic:external_cidrs                  | 0.0.0.0/0                                            |
| apic:nat_type                        | distributed                                          |
| apic:nested_domain_allowed_vlans     |                                                      |
| apic:nested_domain_infra_vlan        |                                                      |
| apic:nested_domain_name              |                                                      |
| apic:nested_domain_node_network_vlan |                                                      |
| apic:nested_domain_service_vlan      |                                                      |
| apic:nested_domain_type              |                                                      |
| apic:svi                             | False                                                |
| apic:synchronization_state           | build                                                |
| availability_zone_hints              |                                                      |
| availability_zones                   |                                                      |
| created_at                           | 2019-05-22T13:38:32Z                                 |
| description                          |                                                      |
| id                                   | 635623ed-5dba-42ec-b3f8-3cff18f925c6                 |
| ipv4_address_scope                   |                                                      |
| ipv6_address_scope                   |                                                      |
| is_default                           | False                                                |
| mtu                                  | 9000                                                 |
| name                                 | external-net-dedicated                               |
| port_security_enabled                | True                                                 |
| project_id                           | cdeda9c674a94394a09e86a2fea498c2                     |
| provider:network_type                | opflex                                               |
| provider:physical_network            | physnet1                                             |
| provider:segmentation_id             |                                                      |
| revision_number                      | 6                                                    |
| router:external                      | True                                                 |
| shared                               | False                                                |
| status                               | ACTIVE                                               |
| subnets                              |                                                      |
| tags                                 |                                                      |
| tenant_id                            | cdeda9c674a94394a09e86a2fea498c2                     |
| updated_at                           | 2019-05-22T13:38:33Z                                 |
+--------------------------------------+------------------------------------------------------+

In Cisco ACI, the command creates a new EPG—EXT-l3out1— and a new bridge domain—EXT-l3out1, as shown in the following screen capture of the Cisco Application Policy Infrastructure Controller (APIC) GUI:


Screen capture from Cisco APIC.
Step 2

Create a Neutron subnet that will be used for SNAT and the floating IP address.

This step is not required if you used --apic:nat_type "" when you created the Neutron external network (because NAT is disabled).

Example:

neutron subnet-create net_name subnet/mask --name subnet_name --disable-dhcp --gateway gateway_ip --apic:snat_host_pool True

The OpFlex agent automatically assigns one IP address for every compute node from the subnet. Virtual machines (VMs) connecting to the external use this IP address (one-to-many NAT) unless they have been assigned with a floating IP address.

The following shows an example of the creation of the external network with NAT enabled

neutron subnet-create external-net-dedicated 10.104.21.0/24 --name ext-subnet --disable-dhcp --gateway 10.104.21.1 --apic:snat_host_pool True
Created a new subnet:
+----------------------------+--------------------------------------------------+
| Field                      | Value                                            |
+----------------------------+--------------------------------------------------+
| allocation_pools           | {"start": "10.104.21.2", "end": "10.104.21.254"} |
| apic:distinguished_names   | {}                                               |
| apic:snat_host_pool        | True                                             |
| apic:synchronization_state | N/A                                              |
| cidr                       | 10.104.21.0/24                                   |
| created_at                 | 2019-05-22T13:38:35Z                             |
| description                |                                                  |
| dns_nameservers            |                                                  |
| enable_dhcp                | False                                            |
| gateway_ip                 | 10.104.21.1                                      |
| host_routes                |                                                  |
| id                         | 238aa55d-1537-4f01-86c9-5f6fc4bde625             |
| ip_version                 | 4                                                |
| ipv6_address_mode          |                                                  |
| ipv6_ra_mode               |                                                  |
| name                       | ext-subnet                                       |
| network_id                 | 635623ed-5dba-42ec-b3f8-3cff18f925c6             |
| project_id                 | cdeda9c674a94394a09e86a2fea498c2                 |
| revision_number            | 0                                                |
| service_types              |                                                  |
| subnetpool_id              |                                                  |
| tags                       |                                                  |
| tenant_id                  | cdeda9c674a94394a09e86a2fea498c2                 |
| updated_at                 | 2019-05-22T13:38:35Z                             |
+----------------------------+--------------------------------------------------+

Creating a SNAT subnet generates a new subnet under the bridge domain, as shown in the following screen capture of the Cisco APIC GUI:


Screen capture from Cisco APIC GUI.
Step 3

(Optional) Assign one or more floating subnets to the external Neutron network:

Example:

neutron subnet-create net_name fip_subnet/mask --name subnet_name --allocation-pool start=start_ip,end=end_ip --disable-dhcp --gateway gateway_ip
The following output and screen capture in the Cisco APIC GUI show an example of the creation of a floating IP subnet:
neutron subnet-create external-net-dedicated 10.104.31.0/24 --name ext-subnet-FIP --allocation-pool start=10.104.31.10,end=10.104.31.100 --disable-dhcp --gateway 10.104.31.1
Created a new subnet:
+----------------------------+---------------------------------------------------+
| Field                      | Value                                             |
+----------------------------+---------------------------------------------------+
| allocation_pools           | {"start": "10.104.31.10", "end": "10.104.31.100"} |
| apic:distinguished_names   | {}                                                |
| apic:snat_host_pool        | False                                             |
| apic:synchronization_state | N/A                                               |
| cidr                       | 10.104.31.0/24                                    |
| created_at                 | 2019-05-22T13:38:38Z                              |
| description                |                                                   |
| dns_nameservers            |                                                   |
| enable_dhcp                | False                                             |
| gateway_ip                 | 10.104.31.1                                       |
| host_routes                |                                                   |
| id                         | 107c2714-2ace-44a7-9cb0-1a7f40ba2833              |
| ip_version                 | 4                                                 |
| ipv6_address_mode          |                                                   |
| ipv6_ra_mode               |                                                   |
| name                       | ext-subnet-FIP                                    |
| network_id                 | 635623ed-5dba-42ec-b3f8-3cff18f925c6              |
| project_id                 | cdeda9c674a94394a09e86a2fea498c2                  |
| revision_number            | 0                                                 |
| service_types              |                                                   |
| subnetpool_id              |                                                   |
| tags                       |                                                   |
| tenant_id                  | cdeda9c674a94394a09e86a2fea498c2                  |
| updated_at                 | 2019-05-22T13:38:38Z                              |
+----------------------------+---------------------------------------------------+

Screen capture from Cisco APIC GUI.
Step 4

Attach the Neutron external network to one OpenStack router as a gateway.

Example:

openstack router set --external-gateway external_net_name router_name

The command creates a contract that allows external connectivity for tenant networks attached to the OpenStack router of the external Neutron network, as shown in the following image:


Diagram of contract for external connectivity

What to do next

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