DHCP High Availability
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You can find the High Availability Settings at **System → High Availability**.

It can be found starting with the **DHCP High Availability Box**.
DHCP is an exception in the High Availability setup since it can only have up to three VT AIR in the setup.
Each additional VT AIR needs to have DHCP disabled, which will be done automatically as long as the settings are enabled on each node.

.. image:: img/HA-DHCP-Config.png
    :width: 100%
    :align: center
    :alt: High Availability DHCP Configuration

You can enable or disable the entire DHCP HA Setup.

**IP Type** it is only supported to have either DHCPv4 or DHCPv6 HA enabled.
This is a current limitation of the DHCP Daemon.

**Role** needs to be set to master on the initial master VT AIR.
There is always only one slave and one backup.
The configuration sync will automatiocally take care of setting the role on the next VT AIR, so you do not need to change the setting on each member.
The role disable will disable DHCP of this type in order for the setup to work properly. Otherwise two DHCP servers will compete to give out leases.

**Syncinterface** should be the sperate sync interface, as all information is synced unencrypted.

**Max Unacked** Specifies how many unacked clients are allowed before this server assumes that the partner is offline and transitions to the partner-down state.
The special value of 0 is allowed for this parameter, which disables the failure-detection mechanism.
In this case, a server that can’t communicate with its partner over the control channel assumes that the partner server is down and transitions to the partner-down state immediately.
The default value of this parameter is 3.

**Master Server** is the IP Address of the master. On the master it will be filled automatically, there is no need to enter it.

**Slave Server** is the IP Address of the slave. On the slave it will be filled automatically, there is no need to enter it.

**Backup Server** is the IP Address of the backup. On the backup it will be filled automatically, there is no need to enter it.

**Associate Firewall Rule** will create the firewall rule to allow the connection between all VT AIR for the DHCP HA Setup. It is highly recommended to enable it.