BIG-IP LTM Nodes: Using FQDN

Important details about the FQDN properties

(1) Auto Populate

• Enabled
  • The system generates an ephemeral node for each IP address returned in response to a DNS query for the FQDN of the node.
  • Additionally, when a DNS response indicates the IP address of an ephemeral node no longer exists, the system deletes the ephemeral node.
• Disabled
  • The system generates an ephemeral node for only one IP address returned in response to a DNS query for the FQDN of the node.
  • Additionally, when there is a change in the IP address returned by DNS server, the system updates the ephemeral node.

(2) Interval

• Specifies the interval (in seconds) in which a query occurs, when the DNS server is up.
• The associated monitor attempts to probe three times, and marks the server down if it there is no response within 3x interval value.
• Note that instead of using an interval value, you can choose to “use TTL” (Time to Live) in the DNS response.

(3) Down Interval

• Specifies the interval (in seconds) in which a query occurs, when the DNS server is down.
• The associated monitor continues polling as long as the DNS server is down.

Nodes Configuration: Using FQDN (Auto Populate: Disabled)

There are 3 possible scenarios:

• FQDN State is “UP”, and DNS Server is reachable (Figure 1)
  • Inside Node – Properties (Figure 2)
  • Node List (Figure 3)
  • TMSH – Node all-properties (Figure 4)
  • TMSH – Ephemeral Node all-properties (Figure 5)
  • TMSH – Ephemeral Node dynamic address (Figure 6)
• FQDN State is “DOWN”, and DNS Server is reachable (Figure 7)
  • TMSH – Node fqdn-up-no-addr (Figure 8)
• FQDN State is “DOWN”, and DNS Server is unreachable (Figure 9)
  • TMSH – Node fqdn-down (Figure 8)

Nodes Configuration: Using FQDN (Auto Populate: Enabled)

• Inside Node – Properties
  • General Properties (Figure 1)
  • FQDN (Figure 2)
• Node List, TMSH – Ephemeral Node List (Figure 3)
• TMSH – Node all-properties (Figure 4)