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Address Assignment Information

General information

Each VM instance interface can have one primary internal IP address, one or more secondary IP addresses, and one external IP address.

Addresses can be static (persistent) or ephemeral (on-persistent):

• Ephemeral external IP addresses:
  • For VM instances, the ephemeral external IP address is also released if you stop the instance. After you restart the instance, it is assigned a new ephemeral external IP address.
• Static external IP addresses:
  • Static external IP address can be reserved and thereby assigned a project indefinitely until they are explicitly released. You can reserve a new static external IP address or promote an existing ephemeral external IP address to a static external IP address.
• Ephemeral internal IP addresses:
  • Ephemeral internal IP addresses remain attached to VM instances until the instance is deleted.
• Static internal IP addresses:
  • For VM instances, static internal IP addresses remain attached to stopped instances until they are removed.

Address Ranges

When creating a VPC and its subnets, subnet address ranges are assigned to these subnets. There are some restriction regarding permitted address ranges:

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• The default gateway does not respond to ping.
• The default gateway does not decrement TTL headers (used for traceroute).
• Only IPv4 unicast traffic is supported.

Interface Configuration on Linux

By default, Google cloud tools installed on the Linux instance automatically start the attached network interfaces and configure them using DHCP.

Should this be undesirable, for example, because a NIC is to be dedicated to the Solaris guest system, this automatic configuration can be suppressed by disabling the setup in the file /etc/default/instance_configs.cfg.

Important information:

• Currently, the Charon-SSP marketplace images are based on CentOS 7.
• NetworkManager is disabled by default in these images.
• If you disable the automatic interface setup as shown above, you must make sure that the correct ifcfg-files for every interface exist in /etc/sysconfig/network-config. Failure to do so, can make your instance unreachable after the next network restart.

To disable automatic interface configuration by the cloud tools, edit the file and set the parameter setup to false as shown in the example below:

# vi /etc/default/instance_configs.cfg[NetworkInterfaces]

dhclient_script = /sbin/google-dhclient-script
dhcp_command =
ip_forwarding = true
setup = false

After restarting the network (systemctl restart network), the configuration as defined in the ifcfg-files should be set for the interfaces.