Network Interfaces

Introduction

Zadara Cloud Services UI supports network configurations for VM instances based on the following common network concepts:

  • Subnets - Standard IP subnet based on IP address and mask.

  • Network Interfaces - A network interface is simply a specific IP address assigned to a VM instance. To help maintain network consistency, a network interface can be defined as an IP on a specific subnet. The UI will ensure that the selected IP is within the selected subnet.

Important

Zadara recommends configuring only one network interface on a VM

A VM connected to more than one Subnet, one of which has an Elastic IP (EIP) attached to its Elastic Network Interface (ENI), might suffer from an unpredictable Internet connectivity problem.

The reason is that the two ENIs receive a DHCP configuration which includes a default GW (i.e. a default route).

For example:

A VM has all of the following configured:

  • A Network Interface on a Direct Subnet

  • A Network Interface on the VPC Public Subnet

  • An Elastic IP associated with the Network Interface on the VPC Public Subnet

  • Security Groups to allow desired Internet traffic to reach the VM via the Elastic IP, for example port 22

As a result, the following symptoms could be expected:

  • There are two listings for default route/0.0.0.0 in the guest VM O/S:

    • One points to the GW on the Direct Subnet

    • One points to the GW on the VPC Public subnet

  • Outbound requests work correctly, such as ping to Internet sites and requests from the VM to external websites.

  • Replies to inbound requests do not work. The VM has two bound network interfaces, but it cannot accept and reply to connections from the Internet via the Elastic IP.

  • If the admin manually deletes the default route/0.0.0.0 in the guest VM pointing to the GW on the Direct Subnet, the inbound Internet connections on the Elastic IP start working. But DHCP refreshes all the time, and it repopulates the entry for the default route/0.0.0.0 to the GW on the Direct Subnet soon after it is manually deleted, effectively reinstating prevention of replies to connections from the Internet via the Elastic IP.

Creating Network Interfaces

To define a network interface:

  1. Navigate to the Networking > Network Interfaces view.

  2. From the top toolbar, click Create.

  3. In the Create Elastic Network Interface dialog, enter the following:

    • Name - name of the network interface.

    • Description - optional description of the network interface.

    • VPC - VPC on which the network interface should be assigned.

    • Subnet - select from an existing subnet configured for the VPC or define a new subnet to be added to the VPC.

    • Private IP - select private IP within the subnet defined above.

    • Security Groups - select security group to control the traffic on the network interface.

      Note

      For more information on security groups, see Security Groups Introduction.

Network Interface Operations

After creation of a network interface, it will be displayed in the network interface list in the Networking > Network Interface view. The following operations can be performed by selecting a network interface from the list, and clicking the appropriate icon.

From top toolbar:

  • Modify - to change the name of the network interface.

  • Security Group - to change the security group associated with the network interface.

  • Delete

  • Detach Subnet - to detach a specific network interface from a VM instance.

  • Soft Reset - rebind all VM ports.

  • Hard Reset - unbind and then rebind all relevant ports.

From lower toolbar:

  • Overview - to see general information related to VM instance associated with the network interface, select Overview tab.

  • Events - to view configuration events (info) or alarms for the network interface, select the Events tab in lower portion of view.