Author: Antxon Gonzalez

VM networks are virtual networks that use a VLAN tag on top of the hypervisor's network interfaces on the physical network.

The physical network interfaces belong to a network service type (NST), which identifies the network segment that the interface is connected to.

To understand Abiquo Cloud networking, you need to take into account these concepts first.

Racks

Before you add a physical machine to a datacenter, you need to create the rack it will belong to.

A rack is a logical set of physical machines providing the same level of compute service.

Each rack also defines a VLAN pool for all the physical machines inside the rack.

This pool is used to provide private networks to virtual datacenters.

Network service type

Every time you add a physical machine, you must choose its rack and specify the network service type (NST) its network interfaces are connected to.

An NST is a set of interfaces providing the same network service level. You may think of each NST as a different network segment.

VLANs inside an NST have the same meaning for interfaces in the same rack, while VLANs will be different for interfaces in different NSTs or racks.

This does not imply that VLANs inside a NST are interconnected, as this depends on the VLAN type.

Cloud networks

Cloud networks in Abiquo are defined by their type, network service type (NST), and VLAN tag. This means that all VMs using a network will run on hypervisors with NICs of the corresponding NST.

There will always be a default NST that we call the Service Network, which is the NST that will hold most of the networking workload.

There are three different kind of networks:

• Private: Bound to the virtual datacenter (VDC) they were created in.
  The VLAN tag is taken from the VLAN pool of a rack automatically, bounding the network workload to it.

• External: Bound to a datacenter and a cloud tenant (enterprise).
  This means that the network VLAN tag has the same meaning for all racks in the datacenter.

• Public: Bound to a datacenter only.
  They are similar to external networks, but more than one enterprise may use them.

Private networks are bound to the rack they were defined in, and their VLAN tags have no meaning outside this rack. This means that VDCs are bound to the rack their private networks are defined in.

External and public networks can be used in all racks in a datacenter. Their VLAN tags must be defined in the infrastructure before you define them inside Abiquo.

VMs in the same enterprise may communicate through public and external networks, or private networks if they belong to the same VDC.

The only way for VMs in different enterprises communicate is through a public network.

DHCP

There are two different approaches to get DHCP working in your environment: Regular DHCP infrastructure or the Abiquo DNSMasq networking solution.

Both solutions require a DHCP service listening to the Abiquo networks VLAN tags in their NSTs, meaning that the service will need a NIC in each network.

DHCP may require a Relay network infrastructure to deal with all networks depending on their number,  while the DNSMasq solution has no limits to the number of interfaces the server may be listening to.

Additionally, DHCP requires an OMAPI capable server, as this is the protocol that Abiquo will use to manage the leases for the network environment.

When using SDN systems, such as NSX-T, Abiquo can use the DHCP services of the SDN system.

If your datacenter is configured without DHCP services, you can use hypervisor tools or cloud-init to assign network addresses. See Guest setup