You are troubleshooting your Dataflow pipeline that processes data from Cloud Storage to BigQuery. You have discovered that the Dataflow worker nodes cannot communicate with one another. Your networki

Question

Options

• ADetermine whether your Dataflow pipeline has a custom network tag set.
• BDetermine whether there is a firewall rule set to allow traffic on TCP ports 12345 and 12346 for the Dataflow network tag.
• CDetermine whether there is a firewall rule set to allow traffic on TCP ports 12345 and 12346 on the subnet used by Dataflow workers.
• DDetermine whether your Dataflow pipeline is deployed with the external IP address option enabled.

• A
  2% (1)
• B
  90% (47)
• C
  2% (1)
• D
  6% (3)

Explanation

Option B is correct because Dataflow workers must communicate with each other over TCP ports 12345 and 12346, and since the networking team manages firewall rules via network tags, the right diagnostic step is to verify that a firewall rule exists allowing traffic on those ports for the Dataflow network tag (by default, dataflow). Without that tag-targeted rule, worker-to-worker communication will be blocked regardless of any other configuration.

Why the distractors are wrong:

• A is a red herring - whether a custom tag exists doesn't tell you if traffic is allowed; you need to verify the firewall rule for whichever tag is in use.
• C is close but violates the team's established practice of using network tags; subnet-based rules bypass tag governance, so this contradicts the "Google-recommended" qualifier in the question.
• D is about outbound internet access for workers, not inter-worker communication, which happens over internal IPs regardless of external IP assignment.

Memory tip: Lock in "12345–12346 = Dataflow worker talk" - these two consecutive ports are Dataflow-specific and almost always appear in exam questions about worker communication. Pair that with the rule: tag-based firewall → check the tag's rule, not the subnet's.

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