Eucalyptus cloud networking modes address two basic questions: Who assigns IP addresses? Can I use advanced features, like VLANs and Security Groups?
The networking modes supported in Eucalyptus are SYSTEM,STATIC, and MANAGED (plus MANAGED-NOVLAN).
SYSTEM is the default networking mode for Eucalyptus clouds. It assumes that virtual machine instances will be assigned IP addresses by an external DHCP server. Eucalyptus clouds in SYSTEM mode can not use Elastic IPs, Security Groups, or VLAN tagging. It is most often used in setting up test environments or proof-of-concepts (POCs).
Static networking mode assumes there are no other DHCP servers on the network. Advanced features such as VLAN tagging, Elastic IPs, and Security Groups are not available. The Eucalyptus cloud assumes responsibility for assigning IP addresses to instances. To do so, each IP address must be manually configured and assigned to a specific manually configured MAC address. Because of the labor-intensive nature of STATIC mode, it rarely gets used, and primarily exists for backwards compatibility reasons.
The two MANAGED networking modes are the most common mode in Eucalyptus cloud deployments. In either of them, the Eucalyptus cloud assumes responsibility for assigning IP addresses to virtual machine instances in a controlled subnet, regardless of the presence of a DHCP server on the corporate network. In addition, the user can configure Elastic IPs, and Security Groups can also be used. The only difference between MANAGED and MANAGED-NOVLAN is that MANAGED mode can utilize VLAN tagging for virtual machine instance isolation, whereas MANAGED-NOVLAN can not.
In the next post we'll discuss storage concepts in Eucalyptus.