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How to Configure DHCP with Dynamic DNS

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Configure dynamic DNS updates for the Barracuda CloudGen Firewall DHCP service. The DDNS update style is evaluated once after reading the dhcpd.conf file, not each time a client is assigned an IP address. As a result, the same DNS update style is used for all clients.

This article gives a general overview of configuring a setup that applies to the title of this article.

At the end of this article, there is a link to an article that illustrates how to do a certain setup based on a discrete practical use case.

NOTE!
The DNS service denies Dynamic DNS updates from DHCP clients in the same network or an external DHCP server.

Before You Begin

  • Before configuring dynamic DNS, enable advanced pool configuration in the DHCP service setup. For more information, see How to Configure Advanced DHCP Settings.

  • Make sure that a DNS service is created and configured on your firewall. For more information, see DNS.

Step 1. Configure the DNS Zones

Configure DNS zones for your clients. If a forward and a reverse lookup must be done, a valid zone must be configured where updates are allowed. A reverse zone is not required if only a forward lookup should be done.

For more information, see How to Configure a Zone.

Step 2. Create a DHCP Subnet

Create a DHCP subnet for the clients that should receive DDNS updates. For more information, see How to Configure DHCP Subnets and Address Pools.

Step 3. Create a Parameter Template

Create a DHCP parameter template for the subnet the clients reside in:

  • In the Dynamic DNS Parameters settings, set Do Fwd Updates to true.

  • For dynamic DNS to work, you must also enter the DDNS Domainname. 
    param_temp.png 

For more information, see How to Configure DHCP Parameter Templates .  

Step 4. Configure Dynamic DNS

  1. Go to CONFIGURATION > Configuration Tree >Box > Assigned Services > DHCP > DHCP Enterprise Configuration .

  2. In the left menu, expand the Configuration Mode section and click Advanced View.

  3. In the left menu, select Dynamic DNS.

  4. Click Lock.

  5. Select whether to use a DNS Update Scheme.

    • When selecting interim, choose an option from the Client Updates list.

      The DHCP server does not necessarily always update both the A and the PTR records. The FQDN (fully qualified domain name) option includes a flag that, when sent by the client, indicates that the client wishes to update its own A record. In that case, the server can be configured either to honor the client's intentions or ignore them. This is done with either statement "allow client-updates" or "ignore client-updates". By default, client updates are ignored.

  6. (optional) In the Zone Keys table, click + and add the HMAC-MD5 keys for the DNS zones.

  7. In the DNS Zones table, click + and add the DNS zones. 

  8. Specify the Zone Type. You can select:

    • Forward – (default) The hostname is looked up.

      • Enter the network of the forward lookup in the Forward Zone Name field.

    • Reverse – The IP address is looked up.

      • Enter the network of the reverse lookup in the Reverse Lookup Net/Netmask fields.

    • Both – IP address and hostname are looked up.

      • Enter the network of the forward and reverse lookup in the Forward Zone Name and Reverse Lookup Net/Netmask fields.

  9. Enter the DNS Server IP address.

  10. Select the Authentication Key for the zone that was entered in the Zone Keys table.

  11. (optional) Click + and add additional DNS zones.

  12. Click OK.

  13. Click Send Changes and Activate.

If you want to configure DHCP with dynamic DNS based on a discrete use case, see Example - How to Configure DHCP with Dynamic DNS.