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Manual Chapter: Setting Up a BIG-IP DNS Redundant System Configuration
Manual Chapter
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Overview: Configuring a BIG-IP DNS redundant system

You can configure BIG-IP® DNS in a redundant system configuration, which is a set of two BIG-IP DNS systems: one operating as the active unit, the other operating as the standby unit. If the active unit goes offline, the standby unit immediately assumes responsibility for managing DNS traffic. The new active unit remains active until another event occurs that would cause the unit to go offline, or you manually reset the status of each unit.

Note: This basic configuration consists of only two BIG-IP DNS devices (active and standby), but the BIG-IP system now allows for a redundant system configuration to contain an arbitrary number of devices within a server.

Task Summary

Perform the following tasks to configure a BIG-IP DNS redundant system configuration.

Before you begin, ensure that the Setup utility was run on both devices. During the Setup process, you create VLANs internal and external and the associated floating and non-floating IP addresses, and VLAN HA and the associated non-floating self IP address. You also configure the devices to be in an active-standby redundant system configuration.

Defining an NTP server

Define a Network Time Protocol (NTP) server that both BIG-IP® DNS systems use during configuration synchronization.
Important: Perform these steps on both the active and standby systems.
  1. On the Main tab, click System > Configuration > Device > NTP .
    The NTP Device configuration screen opens.
  2. For the Time Server Lookup List setting, in the Address field, type the IP address of the NTP that you want to add. Then click Add.
    Note: If you did not disable DHCP before the first boot of the BIG-IP system, and if the DHCP server provides the information about your NTP server, then this field is automatically populated.
  3. For the Time Server List setting, in the Address field, type the IP address of the NTP server that you want to add. Then click Add.
    For this example, type 192.168.5.15.
    Note: If you did not disable DHCP before the first boot of the BIG-IP system, and if the DHCP server provides the information about your NTP server, then this field is automatically populated.
  4. For the Time Server List setting, in the Address field, type the IP address of an NTP server that you want to add. Then click Add.
    Note: If you are using Dynamic Host Configuration Protocol (DHCP) to assign IP addresses, then the BIG-IP system automatically populates the Address field with the fully-qualified domain name (FQDN) of the NTP server.
  5. Repeat the preceding step as needed.
  6. Click Update.
During configuration synchronization, the systems use this time value to determine if any newer configuration files exist.

Creating listeners to identify DNS traffic

Create listeners to identify the DNS traffic that BIG-IP® DNS handles. The best practice is to create four listeners: one with an IPv4 address that handles UDP traffic, and one with the same IPv4 address that handles TCP traffic; one with an IPv6 address that handles UDP traffic, and one with the same IPv6 address that handles TCP traffic.
Note: DNS zone transfers use TCP port 53. If you do not configure listeners for TCP the client might receive the error: connection refused or TCP RSTs.
If you have multiple BIG-IP DNS systems in a device group, perform these steps on only one system.
  1. On the Main tab, click DNS > Delivery > Listeners .
    The Listeners List screen opens.
  2. Click Create.
    The Listeners properties screen opens.
  3. In the Name field, type a unique name for the listener.
  4. For the Destination setting, in the Address field, type an IPv4 address on which BIG-IP DNS listens for network traffic.
  5. In the Service area, from the Protocol list, select UDP.
  6. Click Finished.
Create another listener with the same IPv4 address and configuration, but select TCP from the Protocol list. Then, create two more listeners, configuring both with the same IPv6 address, but one with the UDP protocol and one with the TCP protocol.

Defining a data center

On BIG-IP®DNS, create a data center to contain the servers that reside on a subnet of your network.
  1. On the Main tab, click DNS > GSLB > Data Centers .
    The Data Center List screen opens.
  2. Click Create.
    The New Data Center screen opens.
  3. In the Name field, type a name to identify the data center.
    Important: The data center name is limited to 63 characters.
  4. In the Location field, type the geographic location of the data center.
  5. In the Contact field, type the name of either the administrator or the department that manages the data center.
  6. From the Prober Preference list, select the preferred type of prober(s).
    Option Description
    Inside Data Center By default, select probers inside the data center.
    Outside Data Center Select probers outside the data center.
    Specific Prober Pool Select one of the Probers from the drop-down list. When you want to assign a Prober pool at the data center level.
  7. From the Prober Fallback list, select the type of prober(s) to use if insufficient numbers of the preferred type are available.
    Option Description
    Any Available By default, select any available prober.
    Inside Data Center Select probers inside the data center.
    Outside Data Center Select probers outside the data center.
    None No fallback probers are selected. Prober fallback is disabled.
    Specific Prober Pool Select one of the Probers from the drop-down list. When you want to assign a Prober pool at the data center level.
  8. From the State list, select Enabled.
  9. Click Finished.
Now you can create server objects and assign them to this data center.
Repeat these steps to create additional data centers.

Defining a server and devices on the active BIG-IP system

Ensure that the data centers where the BIG-IP® DNS systems reside exist in the configuration.
Using this procedure, create two servers on the active BIG-IP system, one that represents the active system and one that represents the standby system.
Important: Perform this procedure on only the active system.
  1. On the Main tab, click DNS > GSLB > Servers .
    The Server List screen opens.
  2. Click Create.
    The New Server screen opens.
  3. In the Name field, type a name for the server.
    Important: Server names are limited to 63 characters.
  4. From the Product list, select BIG-IP System.
  5. From the Data Center list, select the data center where the server resides.
  6. From the Prober Preference list, select the preferred type of prober(s).
    Option Description
    Inherit From Data Center By default, a server inherits the prober preference selection assigned to the data center in which the server resides.
    Inside Data Center A server selects the probers from inside the data center where the server resides.
    Outside Data Center A server selects the probers from outside the data center where the server resides.
    Specific Prober Pool Select one of the Prober pools from the drop-down list. When assigning the Prober pool at the server level.
  7. From the Prober Fallback list, select the type of prober(s) to be used if insufficient numbers of the preferred type are available.
    Option Description
    Inherit From Data Center By default, a server inherits the prober fallback selection assigned to the data center in which the server resides.
    Any Available For selecting any available prober.
    Inside Data Center A server selects probers from inside the data center where the server resides.
    Outside Data Center A server selects probers from outside the data center where the server resides.
    None No fallback probers are selected. Prober fallback is disabled.
    Specific Prober Pool Select one of the Probers from the drop-down list. When you want to assign a Prober pool at the server level.
  8. From the State list, select Enabled.
  9. In the BIG-IP System Devices area, add two devices (one that represents the active system and one that represents the standby system).
    1. Click Add.
    2. Type a name in the Device Name field.
    3. Type an external (public) IP address in the Address field.
    4. If you use NAT, type an internal (private) IP address in the Translation field.
    5. Click Add. Repeat the steps to add a second device, which represents the standby system.
    6. Click OK.
  10. From the Virtual Server Discovery list, select Disabled.
  11. Click Finished.
    The Server List screen opens displaying the new server in the list.

Enabling global traffic configuration synchronization

Enable global traffic configuration synchronization options and assign a name to the BIG-IP DNS synchronization group.
  1. On the Main tab, click DNS > Settings > GSLB > General .
    The General configuration screen opens.
  2. Select the Synchronize check box.
  3. In the Group Name field, type the name of the synchronization group.
  4. In the Time Tolerance field, type the maximum age difference in seconds, between the sets of configuration files on the systems in a BIG-IP DNS configuration synchronization group.
  5. Select the Synchronize DNS Zone Files check box.
  6. Click Update.

Running the gtm_add script

You must run the gtm_add script from the standby system.
Note: You must perform this task from the command-line interface.
  1. On the new BIG-IP® DNS system, log in to the command-line interface.
  2. Type gtm_add, and press Enter.
  3. Press the y key to start the gtm_add script.
  4. Type the IP address of the existing BIG-IP DNS system, and press Enter.
The gtm_add script acquires configuration data from the active system; once this process completes, you have successfully created a redundant system consisting of two BIG-IP DNS systems.
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