Ports

A port is a virtual representation of a physical switch-port. That is, a connection between a network (does not have to be a private) and an instance or a router. Ports are generally created on demand by connecting an instance to a subnet (via a network). If you for some reason need to create a port manually, that can also be done (see below). If you do, you also need to assign the port (explicitly) to the instance you want to connect to a network. Remember that a manually created port may not be removed when you remove an instance.

Note

There are only certain special use-cases where you would want to manually create a port. One use case is if you want to assign multiple interfaces to the same network when creating an instance. Its only possible to add a network once, but many ports can be assigned that each connect to the same network.

We recommend sticking to a single port (or interface) on an instance as its generally easier to understand the network flow and plan security that way. Routing should instead be used. If using this network design then adding ports manually should rarely be needed as an instance will have a port created when launched.

Below we will however show how to create ports in the various tools.

Note

Should you opt not to use DHCP to assign IP configuration to a new port (interface), keep in mind that the MTU is also set via DHCP and needs to be set manually in these cases.

Create a port using the cloud management portal

To create a port using the Cloud management portal, follow these steps:

  • Press “Networking” and then “Ports” in the sidebar menu.

  • Press the “+” icon in the bottom right corner.

  • Name your port.

  • Select the private network you want to connect to under “Network”.

  • Select “Subnet” under “Ip address or subnet”. If you would rather manage your IP-configuration on your instance manually (not recommended), you would instead leave “unspecified”.

  • Select the private subnet you want to use.

  • Press “create”.

Create a port using OpenStack Horizon

To create a port using the OpenStack Horizon, follow these steps:

  • Under “project”, click “Network” and then “Networks” in the sidebar menu.

  • Click the name of the network to which you want to add the port.

  • Press the “Ports” tab on the top.

  • Press “Create port”.

  • Name your port.

  • Choose “Subnet” under “Specify IP address or subnet”. If you would rather manage your IP-configuration on your instance manually (not recommended), you would instead leave “unspecified”.

  • Select the private subnet you want to use.

  • Press “Create”.

Create a port using OpenStack terminal client

  • Run this command: openstack network list. Save the name of the network you want to connect to.

  • Run this command: openstack subnet list. Save the name of the subnet you want to use (assuming you want to let the platform configure an IP on the port.

  • Run this command: openstack port create --network [NETWORK NAME] --fixed-ip subnet=[SUBNET NAME] [PORT NAME], replacing the items in angle brackets with the information from the previous steps and the name of the port. If you want to know more options, use “-h” at the end of the command.

Note

Your port is now available for use but remember it will also need to be assigned to an instance before it can be used.