Exam Professional Cloud Network Engineer topic 1 question 177 discussion

Actual exam question from Google's Professional Cloud Network Engineer

Question #: 177
Topic #: 1

[All Professional Cloud Network Engineer Questions]

You have provisioned a Cloud Interconnect connection with a VLAN attachment. You configured Border Gateway Protocol (BGP) between your on-premises router and your Cloud Router. After deploying and testing the connection, you discover that the BGP session is not established between your on-premises router and the Cloud Router. Which two actions should you take to resolve this issue? (Choose two.)

A. From the Google Cloud console, run gcloud compute routers get-status to verify the Address Resolution Protocol (ARP) learned.
B. Verify that you have configured the on-premises router's subinterface with a subnet mask of /31.
C. Verify that you have configured the on-premises router's eBGP multihop with a minimum hop length of 4.
D. Verify that you have configured the on-premises router's BGP security parameters to use MD5 authentication.
E. From the Google Cloud console, run gcloud compute interconnects get-diagnostics to verify the Address Resolution Protocol (ARP) learned.

Show Suggested Answer

Suggested Answer: AB 🗳️

by b0b25 at Feb. 22, 2025, 3:47 a.m.

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n2183712847

1 month, 2 weeks ago

Selected Answer: AD

So, E is definitively wrong for checking ARP. B is likely wrong regarding the /31 mask but correct in pointing to the subnet mask configuration as a check. checking the ARP learned status on the Cloud Router and verifying the MD5 authentication configuration on the on-premises router are valid and common troubleshooting steps for a BGP session not establishing over Cloud Interconnect.

upvoted 1 times

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mohitms1996

2 months, 2 weeks ago

Selected Answer: AE

❌ B. Verify that you have configured the on-premises router's subinterface with a subnet mask of /31. Incorrect approach: Google Cloud uses /29 subnets for VLAN attachments, not /31. A /31 subnet mask is used for point-to-point links but is not applicable for Cloud Interconnect VLAN attachments.

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Popa

2 months, 4 weeks ago

Selected Answer: BE

The correct answers are B and E.

upvoted 1 times

7103685

2 months, 2 weeks ago

(B)Check that the correct IP addresses are allocated for your on-premises router interface and its BGP neighbor. A common mistake is to configure a /30 on your on-premises router interface instead of a /29. Google Cloud reserves all other addresses in the /29 CIDR. (A) Is A correct, because E is only for Dedicated Interconnect.

upvoted 1 times

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RKS_2021

3 months, 2 weeks ago

Selected Answer: AB

(A) gcloud compute routers get-status → This command helps troubleshoot BGP session issues by showing ARP information, learned prefixes, and BGP status. If ARP isn't learned correctly, BGP won't establish. (B) Subnet mask of /31 → Google Cloud uses a /30 or /31 subnet for VLAN attachments. If your on-premises router isn't configured correctly with one of these subnet masks, BGP won't work.

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