101 · Question #305
Which four of the following statements about LDNS probes are true? (Choose four.)
The correct answer is B. They check each requesting LDNS that has made a request of the GTM. D. They are used to develop path metrics. E. They verify the link between a data center and an LDNS. F. Probing only takes place if GTM is configured to use dynamic load balancing.. LDNS probes gather path metrics and verify connectivity between GTM data centers and requesting LDNS servers, and only run when dynamic load balancing is active.
Question
Which four of the following statements about LDNS probes are true? (Choose four.)
Options
- AOnly GTM devices can act as a prober.
- BThey check each requesting LDNS that has made a request of the GTM.
- CThey can determine available cache size on the client.
- DThey are used to develop path metrics.
- EThey verify the link between a data center and an LDNS.
- FProbing only takes place if GTM is configured to use dynamic load balancing.
How the community answered
(61 responses)- A8% (5)
- B75% (46)
- C16% (10)
Why each option
LDNS probes gather path metrics and verify connectivity between GTM data centers and requesting LDNS servers, and only run when dynamic load balancing is active.
Other BIG-IP devices such as LTM can also be designated as probers in a GTM deployment, so the role is not exclusive to GTM devices.
GTM tracks every LDNS server that submits a DNS query and actively probes those specific servers to collect performance data used in intelligent load balancing decisions.
LDNS probes collect network path metrics like RTT and packet loss - they have no mechanism to inspect or report DNS cache capacity on client resolvers.
LDNS probes measure round-trip time and other path metrics between GTM-managed data centers and LDNS servers, providing the data needed for performance-based load balancing methods.
Probes test the health and reachability of the network path between a GTM data center and a requesting LDNS server, ensuring GTM only routes traffic over verified functional paths.
LDNS probing is activated only when GTM is configured to use a dynamic load balancing method such as RTT or completion rate, because static methods do not require live path metric collection.
Concept tested: F5 GTM LDNS probing and dynamic load balancing
Source: https://techdocs.f5.com/kb/en-us/products/big-ip_gtm/manuals/product/gtm-concepts-11-4-0/3.html
Topics
Community Discussion
No community discussion yet for this question.