DevStack Networking¶

An important part of the DevStack experience is networking that works by default for created guests. This might not be optimal for your particular testing environment, so this document tries its best to explain what’s going on.

Defaults¶

If you don’t specify any configuration you will get the following:

neutron (including l3 with openvswitch)
private project networks for each openstack project
a floating ip range of 172.24.4.0/24 with the gateway of 172.24.4.1
the demo project configured with fixed ips on a subnet allocated from the 10.0.0.0/22 range
a br-ex interface controlled by neutron for all its networking (this is not connected to any physical interfaces).
DNS resolution for guests based on the resolv.conf for your host
an ip masq rule that allows created guests to route out

This creates an environment which is isolated to the single host. Guests can get to the external network for package updates. Tempest tests will work in this environment.

Note

By default all OpenStack environments have security group rules which block all inbound packets to guests. If you want to be able to ssh / ping your created guests you should run the following.

openstack security group rule create --proto icmp --dst-port 0 default
openstack security group rule create --proto tcp --dst-port 22 default

Locally Accessible Guests¶

If you want to make your guests accessible from other machines on your network, we have to connect br-ex to a physical interface.

Dedicated Guest Interface¶

If you have 2 or more interfaces on your devstack server, you can allocate an interface to neutron to fully manage. This should not be the same interface you use to ssh into the devstack server itself.

This is done by setting with the PUBLIC_INTERFACE attribute.

[[local|localrc]]
PUBLIC_INTERFACE=eth1

That will put all layer 2 traffic from your guests onto the main network. When running in this mode the ip masq rule is not added in your devstack, you are responsible for making routing work on your local network.

Shared Guest Interface¶

Warning

This is not a recommended configuration. Because of interactions between OVS and bridging, if you reboot your box with active networking you may lose network connectivity to your system.

If you need your guests accessible on the network, but only have 1 interface (using something like a NUC), you can share your one network. But in order for this to work you need to manually set a lot of addresses, and have them all exactly correct.

[[local|localrc]]
PUBLIC_INTERFACE=eth0
HOST_IP=10.42.0.52
FLOATING_RANGE=10.42.0.0/24
PUBLIC_NETWORK_GATEWAY=10.42.0.1
Q_FLOATING_ALLOCATION_POOL=start=10.42.0.250,end=10.42.0.254

In order for this scenario to work the floating ip network must match the default networking on your server. This breaks HOST_IP detection, as we exclude the floating range by default, so you have to specify that manually.

The PUBLIC_NETWORK_GATEWAY is the gateway that server would normally use to get off the network. Q_FLOATING_ALLOCATION_POOL controls the range of floating ips that will be handed out. As we are sharing your existing network, you’ll want to give it a slice that your local dhcp server is not allocating. Otherwise you could easily have conflicting ip addresses, and cause havoc with your local network.

Private Network Addressing¶

The private networks addresses are controlled by the IPV4_ADDRS_SAFE_TO_USE and the IPV6_ADDRS_SAFE_TO_USE variables. This allows users to specify one single variable of safe internal IPs to use that will be referenced whether or not subnetpools are in use.

For IPv4, FIXED_RANGE and SUBNETPOOL_PREFIX_V4 will just default to the value of IPV4_ADDRS_SAFE_TO_USE directly.

For IPv6, FIXED_RANGE_V6 will default to the first /64 of the value of IPV6_ADDRS_SAFE_TO_USE. If IPV6_ADDRS_SAFE_TO_USE is /64 or smaller, FIXED_RANGE_V6 will just use the value of that directly. SUBNETPOOL_PREFIX_V6 will just default to the value of IPV6_ADDRS_SAFE_TO_USE directly.

SSH access to instances¶

To validate connectivity, you can create an instance using the $PRIVATE_NETWORK_NAME network (default: private), create a floating IP using the $PUBLIC_NETWORK_NAME network (default: public), and attach this floating IP to the instance:

openstack keypair create --public-key ~/.ssh/id_rsa.pub test-keypair
openstack server create --network private --key-name test-keypair ... test-server
fip_id=$(openstack floating ip create public -f value -c id)
openstack server add floating ip test-server ${fip_id}

Once done, ensure you have enabled SSH and ICMP (ping) access for the security group used for the instance. You can either create a custom security group and specify it when creating the instance or add it after creation, or you can modify the default security group created by default for each project. Let’s do the latter:

openstack security group rule create --proto icmp --dst-port 0 default
openstack security group rule create --proto tcp --dst-port 22 default

Finally, SSH into the instance. If you used the Cirros instance uploaded by default, then you can run the following:

openstack server ssh test-server -- -l cirros

This will connect using the cirros user and the keypair you configured when creating the instance.

Remote SSH access to instances¶

You can also SSH to created instances on your DevStack host from other hosts. This can be helpful if you are e.g. deploying DevStack in a VM on an existing cloud and wish to do development on your local machine. There are a few ways to do this.

Configure instances to be locally accessible

The most obvious way is to configure guests to be locally accessible, as described above. This has the advantage of requiring no further effort on the client. However, it is more involved and requires either support from your cloud or some inadvisable workarounds.

Use your DevStack host as a jump host

You can choose to use your DevStack host as a jump host. To SSH to a instance this way, pass the standard -J option to the openstack ssh / ssh command. For example:

openstack server ssh test-server -- -l cirros -J username@devstack-host

(where test-server is name of an existing instance, as described previously, and username and devstack-host are the username and hostname of your DevStack host).

This can also be configured via your ~/.ssh/config file, making it rather effortless. However, it only allows SSH access. If you want to access e.g. a web application on the instance, you will need to configure an SSH tunnel and forward select ports using the -L option. For example, to forward HTTP traffic:

openstack server ssh test-server -- -l cirros -L 8080:username@devstack-host:80

(where test-server is name of an existing instance, as described previously, and username and devstack-host are the username and hostname of your DevStack host).

As you can imagine, this can quickly get out of hand, particularly for more complex guest applications with multiple ports.

Use a proxy or VPN tool

You can use a proxy or VPN tool to enable tunneling for the floating IP address range of the $PUBLIC_NETWORK_NAME network (default: public) defined by $FLOATING_RANGE (default: 172.24.4.0/24). There are many such tools available to do this. For example, we could use a useful utility called shuttle. To enable tunneling using shuttle, first ensure you have allowed SSH and HTTP(S) traffic to your DevStack host. Allowing HTTP(S) traffic is necessary so you can use the OpenStack APIs remotely. How you do this will depend on where your DevStack host is running. Once this is done, install sshuttle on your localhost:

sudo apt-get install sshuttle || yum install sshuttle

Finally, start sshuttle on your localhost using the floating IP address range. For example, assuming you are using the default value for $FLOATING_RANGE, you can do:

sshuttle -r username@devstack-host 172.24.4.0/24

(where username and devstack-host are the username and hostname of your DevStack host).

You should now be able to create an instance and SSH into it:

openstack server ssh test-server -- -l cirros

(where test-server is name of an existing instance, as described previously)