Author: Antxon Gonzalez

VM networks are Virtual Networks which use a VLAN tag on top of the Hypervisors Networks Interfaces physical Network.

The Physical Network Interfaces belong to a Network Service Type (NST), which identifies the Network Segment the Interface is connected to.

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

Racks

Before you add an Physical Machine to a Datacenter, you need to create the Rack it will belong to.

A rack is a logical set of Physcal Machines providing the same compute level service.

Each rack defines also a VLAN pool for all the 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.

A NST is a set of Interfaces providing the same network service level. You may think that each one is a Network Segment different from the others.

VLANs inside a NST have the same meaning for interfaces in the same rack, while it may 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 its type, NST and VLAN tag. This forces VMs using them to run in 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.
  Their VLAN tag is taken from the VLAN pool of a rack automatically, bounding the network workload to it.
  
  
• External: Bound to a Datacenter and an 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 may be used by different enterprises at the same time.

Private networks are bound to the racks they were defined in, and their VLAN tags have no meaning outside it. This in fact bounds VDCs to the rack their privates networks are defined in.

External and public networks instead have the same meaning in all the racks. Their VLAN tag must be defined in the NST infrastructure before defining them inside Abiquo.

VMs in the same enterprise may talk to each other through public an external networks, or private networks is they belong to the same VDC.

The only way for VMs in different enterprises to talk to each other is through public network instead.

DHCP

There are two different approaches to get DHCP working on your environment: Regular DHCP infrastructure or 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 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