101 · Question #105
When DNS_REV is used as the probe protocol by the GTM System, which information is expected in the response from the probe?
The correct answer is C. the FQDN of the local DNS being probed for metric information. The DNS_REV probe protocol is used by GTM to gather latency metrics from local DNS servers by sending a reverse lookup and expecting the probed server to return its own FQDN in the response.
Question
When DNS_REV is used as the probe protocol by the GTM System, which information is expected in the response from the probe?
Options
- Aa reverse name lookup of the GTM System
- Bthe list of root servers known by the local DNS
- Cthe FQDN of the local DNS being probed for metric information
- Dthe revision number of BIND running on the requesting DNS server
How the community answered
(47 responses)- B2% (1)
- C94% (44)
- D4% (2)
Why each option
The DNS_REV probe protocol is used by GTM to gather latency metrics from local DNS servers by sending a reverse lookup and expecting the probed server to return its own FQDN in the response.
A reverse name lookup of the GTM System itself is not what DNS_REV returns - the probe targets the local DNS server and expects that server's own FQDN in the response.
A list of root servers is returned in response to a DNS NS query for the root zone, not as a result of a DNS_REV probe.
When the GTM System uses DNS_REV as the probe protocol, it sends a reverse DNS query to the local DNS server being probed. The expected response is the FQDN of that local DNS server, which confirms it is reachable and responding. This allows GTM to collect Round Trip Time and availability metrics from the local DNS to make intelligent load balancing decisions.
The BIND revision number is returned by a DNS CHAOS class version query, which is a different probe type entirely and unrelated to DNS_REV.
Concept tested: GTM DNS_REV probe protocol expected response
Source: https://techdocs.f5.com/en-us/bigip-14-1-0/big-ip-dns-implementations/monitoring-big-ip-dns-objects.html
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