Chapter 3. Common administrative tasks

Create a network to give your instances a place to communicate with each other and receive IP addresses using DHCP. A network can also be integrated with external networks in your RHEL OpenStack Platform deployment or elsewhere, such as the physical network. This integration allows your instances to communicate with, and be reachable by, outside systems. To integrate your network with your physical external network, see section: “Bridge 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 would 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 wishes to communicate with another subnet must have their traffic directed by a router. Consider placing systems that will require a high volume of traffic amongst themselves in the same subnet, so that they don’t require routing, and avoid the subsequent latency and load.

1. In the dashboard, select Project > Network > Networks.

2. Click +Create Network and specify the following:

3. Click the Next button, and specify the following in the Subnet tab:

4. Click Next to specify DHCP options:

5. Click Create.

The completed network is available for viewing in the Networks tab. You can also click Edit to change any options as needed. Now when you create instances, you can configure them now to use its subnet, and they will subsequently receive any specified DHCP options.

Advanced network options are available for administrators, when creating a network from the Admin view. These options define the network type to use, and allow tenants to be specified:

1. In the dashboard, select Admin > Networks > Create Network > Project. Select a destination project to host the new network using Project.

2. Review the options in Provider Network Type:

Click Create Network, and review the Project’s Network Topology to validate that the network has been successfully created.

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:

1. In the dashboard, select Project > Network > Routers.

2. Click on your virtual router’s name in the Routers list, and click +Add Interface. In the Subnet list, select the name of your new subnet. You can optionally specify an IP address for the interface in this field.

3. Click Add Interface.

Instances on your network are now able to communicate with systems outside the subnet.

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. In order to successfully delete a network, you must first remove or detach any interfaces where it is still in use. The following procedure provides the steps for deleting a network in your project, together with any dependent interfaces.

1. In the dashboard, select Project > Network > Networks. Remove all router interfaces associated with the target network’s subnets. To remove an interface: Find the ID number of the network you would like to delete by clicking on your target network in the Networks list, and looking at the its ID field. All the network’s associated subnets will share this value in their Network ID field.

2. Select Project > Network > Routers, click on your virtual router’s name in the Routers list, and locate the interface attached to the subnet you would like to delete. You can distinguish it from the others by the IP address that would have served as the gateway IP. In addition, you can further validate the distinction by ensuring that the interface’s network ID matches the ID you noted in the previous step.

3. Click the interface’s Delete Interface button.

Select Project > Network > Networks, and click the name of your network. Click the target subnet’s Delete Subnet button.

4. Select Project > Network > Networks, and select the network you would like to delete.

5. Click Delete Networks.

Subnets are the means by which instances are granted network connectivity. 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. Subnets are created in pre-existing networks. Remember that tenant networks in OpenStack Networking can host multiple subnets. This is useful if you intend to host distinctly different systems in the same network, and would 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 wishes to communicate with another subnet must have their traffic directed by a router. Consider placing systems that will require a high volume of traffic amongst themselves in the same subnet, so that they don’t require routing, and avoid the subsequent latency and load.

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. This procedure demonstrates how to delete a specific subnet in a network:

In the dashboard, select Project > Network > Networks, and click the name of your network. Select the target subnet and click Delete Subnets.

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 out in the physical network. Routers and subnets connect using interfaces, with each subnet requiring its own interface to the router. A router’s default gateway 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.

1. In the dashboard, select Project > Network > Routers, and click +Create Router.

2. Enter a descriptive name for the new router, and click Create router.

3. Click Set Gateway next to the new router’s entry in the Routers list.

4. In the External Network list, specify the network that will receive traffic destined for an external location.

5. Click Set Gateway. After adding a router, the next step is to configure any subnets you have created to send traffic using this router. You do this by creating interfaces between the subnet and the router.

You can delete a router if it has no connected interfaces. This procedure describes the steps needed to first remove a router’s interfaces, and then the router itself.

1. In the dashboard, select Project > Network > Routers, and click on the name of the router you would like to delete.

2. Select the interfaces of type Internal Interface. Click Delete Interfaces.

3. From the Routers list, select the target router and click Delete Routers.

Interfaces allow you to interconnect routers with subnets. As a result, the router can direct any traffic that instances send to destinations outside of their intermediate subnet. This procedure adds a router interface and connects it to a subnet. The procedure uses the Network Topology feature, which displays a graphical representation of all your virtual router and networks and enables you to perform network management tasks.

1. In the dashboard, select Project > Network > Network Topology.

2. Locate the router you wish to manage, hover your mouse over it, and click Add Interface.

3. Specify the Subnet to which you would like to connect the router. You have the option of specifying an IP Address. The address is useful for testing and troubleshooting purposes, since a successful ping to this interface indicates that the traffic is routing as expected.

4. Click Add interface.

The Network Topology diagram automatically updates to reflect the new interface connection between the router and subnet.

You can remove an interface to a subnet if you no longer require the router to direct its traffic. This procedure demonstrates the steps required for deleting an interface:

1. In the dashboard, select Project > Network > Routers.

2. Click on the name of the router that hosts the interface you would like to delete.

3. Select the interface (will be of type Internal Interface), and click Delete Interfaces.

You can use procedures in this section to manage your IP address allocation in OpenStack Networking.

# neutron subnet-create --name SUBNET_NAME --enable_dhcp=False --allocation_pool start=IP_ADDRESS,end=IP_ADDRESS --gateway=IP_ADDRESS NETWORK_NAME CIDR

# neutron subnet-create --name public_subnet --enable_dhcp=False --allocation_pool start=192.168.100.20,end=192.168.100.100 --gateway=192.168.100.1 public 192.168.100.0/24

# nova floating-ip-associate INSTANCE_NAME IP_ADDRESS

# nova floating-ip-associate corp-vm-01 192.168.100.20

# neutron floatingip-create public
+---------------------+--------------------------------------+
| Field               | Value                                |
+---------------------+--------------------------------------+
| fixed_ip_address    |                                      |
| floating_ip_address | 192.168.100.20                       |
| floating_network_id | 7a03e6bc-234d-402b-9fb2-0af06c85a8a3 |
| id                  | 9d7e2603482d                         |
| port_id             |                                      |
| router_id           |                                      |
| status              | ACTIVE                               |
| tenant_id           | 9e67d44eab334f07bf82fa1b17d824b6     |
+---------------------+--------------------------------------+

# neutron port-list
+--------+------+-------------+--------------------------------------------------------+
| id     | name | mac_address | fixed_ips                                              |
+--------+------+-------------+--------------------------------------------------------+
| ce8320 |      | 3e:37:09:4b | {"subnet_id": "361f27", "ip_address": "192.168.100.2"} |
| d88926 |      | 3e:1d:ea:31 | {"subnet_id": "361f27", "ip_address": "192.168.100.5"} |
| 8190ab |      | 3e:a3:3d:2f | {"subnet_id": "b74dbb", "ip_address": "10.10.1.25"}|
+--------+------+-------------+--------------------------------------------------------+

# neutron floatingip-associate 9d7e2603482d 8190ab

OpenStack Networking supports one floating IP pool per L3 agent. Therefore, scaling out your L3 agents allows you to create additional floating IP pools.

The procedure below enables you to bridge your virtual network to the physical network to enable connectivity to and from virtual instances. In this procedure, the example physical eth0 interface is mapped to the br-ex bridge; the virtual bridge acts as the intermediary between the physical network and any virtual networks. As a result, all traffic traversing eth0 uses the configured Open vSwitch to reach instances. Map a physical NIC to the virtual Open vSwitch bridge (for more information, see Chapter 14, Configure Bridge Mappings):

# vi /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
TYPE=OVSPort
DEVICETYPE=ovs
OVS_BRIDGE=br-ex
ONBOOT=yes

Configure the virtual bridge with the IP address details that were previously allocated to eth0:

# vi /etc/sysconfig/network-scripts/ifcfg-br-ex
DEVICE=br-ex
DEVICETYPE=ovs
TYPE=OVSBridge
BOOTPROTO=static
IPADDR=192.168.120.10
NETMASK=255.255.255.0
GATEWAY=192.168.120.1
DNS1=192.168.120.1
ONBOOT=yes

You can now assign floating IP addresses to instances and make them available to the physical network.