Scenario: A Citrix Administrator executed the command below in an active-active, global server load balancing (GSLB) setup. set gsib parameter -IdnsprobeOrder DNS PING TCP The order to calculate the…

The correct answer is A. Round-trip time (RTT). Option A (Round-trip time) is correct because the -IdnsprobeOrder parameter in Citrix GSLB specifically defines the sequence of probing methods used to calculate RTT for dynamic proximity-based load balancing. When Citrix ADC determines which data center is "closest" (lowest…

Load Balancing

Question

Scenario: A Citrix Administrator executed the command below in an active-active, global server load balancing (GSLB) setup. set gsib parameter –IdnsprobeOrder DNS PING TCP The order to calculate the __________ for dynamic proximity will be the DNS UDP query followed by the ping and then TCP. (Choose the correct option to complete the sentence.)

Options

ARound-trip time (RTT)
BMultiple IP responses (MIR)
CEmpty Domain Service (EDS)
DTime to live (TTL)

How the community answered

(43 responses)

A
74% (32)
B
5% (2)
C
14% (6)
D
7% (3)

Explanation

Option A (Round-trip time) is correct because the -IdnsprobeOrder parameter in Citrix GSLB specifically defines the sequence of probing methods used to calculate RTT for dynamic proximity-based load balancing. When Citrix ADC determines which data center is "closest" (lowest latency) to a client, it measures RTT using the specified probe methods in order - in this case, DNS UDP query first, then PING, then TCP - falling back to the next method if the previous one fails or is unavailable.

Why the distractors are wrong:

B (MIR) refers to returning multiple IP addresses in a single DNS response, a GSLB method unrelated to probe ordering.
C (EDS) is a mechanism where a GSLB site returns an empty DNS response to signal it cannot serve traffic, also unrelated to probe sequencing.
D (TTL) controls how long a DNS record is cached by resolvers - it has nothing to do with measuring network proximity or latency.

Memory tip: Associate IdnsprobeOrder with "I'm probing to measure travel time" - probes (DNS, PING, TCP) are active measurements of network latency, and latency = Round-Trip Time. If it's measuring how fast, it's RTT.

Topics

#GSLB#Round-Trip Time#Dynamic Proximity#Probe Methods

Community Discussion

Wesley A.May 28, 2026

A is the one you want here. The IdnsprobeOrder parameter controls the sequence of probes used to measure round-trip time for dynamic proximity, so DNS UDP, ping, and TCP are just the three methods NetScaler tries in order to get that RTT measurement, falling back to the next if the previous one fails.

Fatima Z.Jun 4, 2026

Think of it this way, the probe order you set is just the lineup of messengers Citrix sends out to MEASURE how fast the round trip is, so the answer is basically hiding in the word "proximity" itself, because how do you measure closeness if not by timing the journey there and back? My question is, does anyone know if Citrix falls back to the next probe in the order only when the first one fails, or does it always run all three and then average the results to get that RTT figure?

Wesley A.Jun 6, 2026

Citrix runs them in order and falls back only on failure, so that probe list is a priority chain, not a sampling pool, and mixing those two up on the exam is exactly the kind of one-word swap that burned me the first time.

Nina C.Jun 19, 2026

I almost picked D because I kept associating DNS with TTL the moment I saw that parameter, but then I reminded myself that IdnsprobeOrder is specifically controlling how the appliance probes to measure network latency between the client and each GSLB site. That latency measurement is round-trip time, which is exactly what dynamic proximity relies on to route the client to the closest data center, so A is the right fill-in.

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