Chapter 3. Managing project networks

When you plan your Red Hat OpenStack Platform deployment, you start with a number of subnets, from which you allocate individual IP addresses. When you use multiple subnets you can segregate traffic between systems into VLANs.

For example, it is ideal that your management or API traffic is not on the same network as systems that serve web traffic. Traffic between VLANs travels through a router where you can implement firewalls to govern traffic flow.

You must plan your VLANs as part of your overall plan that includes traffic isolation, high availability, and IP address utilization for the various types of virtual networking resources in your deployment.

You can allocate separate VLANs for the different types of network traffic that you want to host. For example, you can have separate VLANs for each of these types of networks. Only the External network must be routable to the external physical network. In this release, director provides DHCP services.

The following systems consume IP addresses from your allocated range:

The following virtual resources consume IP addresses in OpenStack Networking. These resources are considered local to the cloud infrastructure, and do not need to be reachable by systems in the external physical network:

To allow traffic to be routed to and from your new network, you must add its subnet as an interface to an existing virtual router:

This example shows a number of networks that accommodate multiple subnets, with each subnet being assigned a range of IP addresses:

Create a network so that your instances can communicate with each other and receive IP addresses using DHCP. For more information about external network connections, see Bridging the physical network.

When creating networks, it is important to know that networks can host multiple subnets. This is useful if you intend to host distinctly different systems in the same network, and prefer a measure of isolation between them. For example, you can designate that only webserver traffic is present on one subnet, while database traffic traverses another. Subnets are isolated from each other, and any instance that wants to communicate with another subnet must have their traffic directed by a router. Consider placing systems that require a high volume of traffic amongst themselves in the same subnet, so that they do not require routing, and can avoid the subsequent latency and load.

Use subnets to grant network connectivity to instances. Each instance is assigned to a subnet as part of the instance creation process, therefore it’s important to consider proper placement of instances to best accommodate their connectivity requirements.

You can create subnets only in pre-existing networks. Remember that project networks in OpenStack Networking can host multiple subnets. This is useful if you intend to host distinctly different systems in the same network, and prefer a measure of isolation between them.

For example, you can designate that only webserver traffic is present on one subnet, while database traffic traverse another.

Subnets are isolated from each other, and any instance that wants to communicate with another subnet must have their traffic directed by a router. Therefore, you can lessen network latency and load by grouping systems in the same subnet that require a high volume of traffic between each other.

To create a subnet, follow these steps:

OpenStack Networking provides routing services using an SDN-based virtual router. Routers are a requirement for your instances to communicate with external subnets, including those in the physical network. Routers and subnets connect using interfaces, with each subnet requiring its own interface to the router.

The default gateway of a router defines the next hop for any traffic received by the router. Its network is typically configured to route traffic to the external physical network using a virtual bridge.

To create a router, complete the following steps:

Use the openstack project purge command to delete all resources that belong to a particular project as well as deleting the project, too.

For example, to purge the resources of the test-project project, and then delete the project, run the following commands:

# openstack project list
+----------------------------------+--------------+
| ID                               | Name         |
+----------------------------------+--------------+
| 02e501908c5b438dbc73536c10c9aac0 | test-project |
| 519e6344f82e4c079c8e2eabb690023b | services     |
| 80bf5732752a41128e612fe615c886c6 | demo         |
| 98a2f53c20ce4d50a40dac4a38016c69 | admin        |
+----------------------------------+--------------+

# openstack project purge --project 02e501908c5b438dbc73536c10c9aac0

You can delete a router if it has no connected interfaces.

To remove its interfaces and delete a router, complete the following steps:

You can delete a subnet if it is no longer in use. However, if any instances are still configured to use the subnet, the deletion attempt fails and the dashboard displays an error message.

Complete the following steps to delete a specific subnet in a network:

There are occasions where it becomes necessary to delete a network that was previously created, perhaps as housekeeping or as part of a decommissioning process. You must first remove or detach any interfaces where the network is still in use, before you can successfully delete a network.

To delete a network in your project, together with any dependent interfaces, complete the following steps: