# DHCP Option Sets

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## Introduction

A DHCP options set is a set of network configurations that will be delivered
to your VM instance when its interface acquires an IP address using the DHCP
protocol.

1. DHCP options sets are associated with a project so that you can use them
   across all of your virtual private clouds (VPC).
2. The supported options for a DHCP options set are as follows:
   1. **Domain-name-servers** - The IP addresses of up to four domain name
      servers, or ZadaraIaaSProvidedDNS. The default DHCP option set specifies
      ZadaraIaaSProvidedDNS. Although the custom DNS server is used,
      the DHCP-supplied DNS server to the VM instances will always be
      ZadaraIaaSProvidedDNS and the custom DNS will be queried indirectly by
      ZadaraIaaSProvidedDNS.
   2. **Domain-name** - This value is used to complete unqualified DNS hostnames.
      This is set by default to ‘symphony.local’.
   3. **NTP-servers** - The IP addresses of up to four Network Time Protocol
      (NTP) servers.
   4. **Netbios-name-servers** - The IP addresses of up to four NetBIOS name
      servers.
   5. **Netbios-node-type** - The NetBIOS node type (1, 2, 4, or 8).

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### How VPC passes DNS Servers via DHCP

When VPC DNS is **enabled**, the VPC DHCP service provides VMs
with a pair of internal IPs as DNS servers.
The VPC DNS service will look up any local zone records internally,
and it will forward queries to the DNS servers provided in the
DHCP Option Set for all external domains.

When VPC DNS is **disabled**, the VPC DHCP service provides VMs with the
exact IPs of the DNS servers configured in the DHCP Option Set.
In this case, DNS requests will go directly from VMs to the external DNS
nameservers.

## Creating a DHCP Option Set

**To create a DHCP Option Set:**

1. Navigate to the **Networking > DHCP Option Sets** view.
2. From the top toolbar, click **Create**.
3. In the **Create DHCP Options** dialog, enter the following in the
   appropriate tab.
   * **Details** tab:
     - **Name** - name of the DHCP Options Set.
     - **Description** - optional description of the DHCP Options Set.
     - **DNS Domain** - valid DNS domain name (e.g. xxx.com)
   * **Servers** tab:
     - **DNS Servers** - IP of DNS Server associated with DHCP Options set
       being defined. Definition of DNS Server is optional.
     - **NTP Servers** - IP of NTP Server associated with DHCP Options set
       being defined. Definition of NTP Server is optional.
   * **Netbios** tab:
     - **Netbios Node Type** - The following types may be selected:
       - **Type 1** - B-Node
       - **Type 2** - P-Node
       - **Type 4** - M-Node
       - **Type 8** - H-Node
4. Click **Finish**.

## DHCP Options Set Operations

After creation of a DHCP Options Set, it will be displayed in the list
in the **Networking > DHCP Options Set** view. The following operations can
be performed by selecting a DHCP Options Set from the list, and clicking the
appropriate icon from the top toolbar:

* **Modify** - change name of the DHCP options set.
* **Attach VPC** - attach DHCP options set to VPC.
* **Detach VPC** - detach DHCP options set to VPC.
* **Delete** - delete DHCP options set.