Private networking

Private networking gives you control over the networking setup for your instance(s) and is considered the preferred method for launching instances. Also, providers these days are increasingly requiring use of private networks. All CloudBridge deployed VMs must be deployed into a particular subnet.

If you do not explicitly specify a private network to use when launching an instance, CloudBridge will attempt to use a default one. A ‘default’ network is one tagged as such by the native API. If such tag or functionality does not exist, CloudBridge will look for one with a predefined name (by default, called ‘CloudBridgeNet’, which can be overridden with environment variable CB_DEFAULT_NETWORK_NAME).

Once a VM is deployed, cloudbridge’s networking capabilities must address several common scenarios.

  1. Allowing internet access from a launched VM

    In the simplest scenario, a user may simply want to launch an instance and allow the instance to access the internet.

  2. Allowing internet access to a launched VM

    Alternatively, the user may want to allow the instance to be contactable from the internet. In a more complex scenario, a user may want to deploy VMS into several subnets, and deploy a gateway, jump host or bastion host to access other VMs which are not directly connected to the internet. In the latter scenario, the gateway/jump host/bastion host will need to be contactable over the internet.

  3. Secure access between subnets for n-tier applications

    In this third scenario, a multi-tier app may be deployed into several subnets depending on their tier. For example, consider the following scenario:

    • Tier 1/Subnet 1 - Web Server Needs to be externally accessible over the internet. However, in this particular scenario, the web server itself does not need access to the internet.
    • Tier 2/Subnet 2 - Application Server The Application server must only be able to communicate with the database server in Subnet 3, and receive communication from the Web Server in Subnet 1. However, we assume a special case here where the application server needs to access the internet.
    • Tier 3/Subnet 3 - Database Server The database server must only be able to receive incoming traffic from Tier 2, but must not be able to make outgoing traffic outside of its subnet.

    At present, CloudBridge does not provide support for this scenario, primarily because OpenStack’s FwaaS (Firewall-as-a-Service) is not widely available.

1. Allowing internet access from a launched VM

Creating a private network is a simple, one-line command but appropriately connecting it so that it has uniform Internet access across all providers is a multi-step process: (1) create a network; (2) create a subnet within this network; (3) create a router; (4) attach the router to the subnet and (5) attach the router to the internet gateway.

When creating a network, we need to set an address pool. Any subsequent subnets you create must have a CIDR block that falls within the parent network’s CIDR block. Below, we’ll create a subnet starting from the beginning of the block and allow up to 16 IP addresses within a subnet (/28).

net = provider.networking.networks.create(
    name='my-network', cidr_block='10.0.0.0/16')
sn = net.create_subnet(name='my-subnet', cidr_block='10.0.0.0/28', zone=zone)
router = provider.networking.routers.create(network=net, name='my-router')
router.attach_subnet(sn)
gateway = net.gateways.get_or_create_inet_gateway()
router.attach_gateway(gateway)

2. Allowing internet access to a launched VM

The additional step that’s required here is to assign a floating IP to the VM:

net = provider.networking.networks.create(
    name='my-network', cidr_block='10.0.0.0/16')
sn = net.create_subnet(name='my-subnet', cidr_block='10.0.0.0/28', zone=zone)

vm = provider.compute.instances.create('my-inst', subnet=sn, zone=zone, ...)

router = provider.networking.routers.create(network=net, name='my-router')
router.attach_subnet(sn)
gateway = net.gateways.get_or_create_inet_gateway()
router.attach_gateway(gateway)

fip = provider.networking.floating_ips.create()
vm.add_floating_ip(fip)

Retrieve an existing private network

If you already have existing networks, we can query for it:

provider.networking.networks.list()  # Find a desired network ID
net = provider.networking.networks.get('desired network ID')