Configuring DHCP

For Abiquo private, external and public networks, the platform can manage their corresponding VLANs with an ISC DHCP server. Abiquo recommends one DHCP server per physical datacenter. Add the DHCP service to Abiquo when creating or editing a datacenter. You can use the Remote Services DHCP server supplied with Abiquo or another compatible server. If you have many virtual networks, you might need a separate relay server to manage VLANs for the DHCP server. For unmanaged networks, you do not need to configure a DHCP server and you must provide the network addresses to the virtual machines outside of Abiquo.

How Abiquo uses DHCP

Abiquo standard VLAN management has the following features:

• Virtual networks as separate VLANs
• The Cloud Administrator defines VLAN tag pools in Abiquo when creating the racks
• External and public networks are created in the infrastructure and define in Abiquo later
• Private networks will be defined by Abiquo from the racks VLAN tag pools

The connections in DHCP are as follows:

1. When you deploy a virtual machine, Abiquo (Remotes Services) supplies the network settings for the new VM to the DHCP Server.
2. When the new virtual machine powers on, it broadcasts a DHCP request for network configuration.
3. The hypervisor passes the DHCP request through a VLAN to the DHCP server.
4. The DHCP server broadcasts a lease with the network configuration for the virtual machine over the same VLAN

DHCP infrasctructure

When configuring the DHCP infrastructure, there are several choices depending on the number of VLANs in the environment:

1. DHCP Server only, for < 200 VLANs.
   The Server listens to all VLANs. We recommend using a dedicated DHCP Server for this configuration.
   
   

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2. DHCP Server with DHCP Relay, for < 1000 VLANs.
   The relay server listens on all the VLANs and forwards the DHCP requests to the Server.
   In this configuration you can use the DHCP server on the Remote Services server. Do not configure support for VLANs on the DHCP Server.
   
   

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3. DHCP Server with multiple DHCP Relays, for > 1000 VLANs.
   Multiple DHCP relay servers allow you to create large networks in a hierarchical forwarding structure.
   
   

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The server managing a VLAN (DHCP Relay or DHCP Server) must have one interface with IP in the VLAN that will identify the VLAN in the DHCP Server. 

To configure a single DHCP server with VLAN support, see Configuring a DHCP Server. 

To install a DHCP Relay server with the Abiquo appliances see Automatically Configuring One DHCP Relay Server.

These configurations are designed for multiple VLAN networks, which by definition have separate VLAN tags and isolate DHCP broadcasts. The DHCP Server and VM communicate through broadcasts, which are also relayed, until the IP address of the VM is set, so there is no specific requirement for the IP address of the VNIC or NIC. However, it is recommended that the IP address range used for the VNICs or NICs is not part of any other networks. For example, you could use the upper range of the management network. If you have complex requirements, you may need to adapt these configurations.

If you need to use multiple relay servers, see Manually Configuring Multiple DHCP Relay Servers