Google Professional Cloud Network Engineer Question 743
Select 4Google Cloud PlatformYour organization has set up a site-to-site VPN between its on-premises data center and a VPC network in Google Cloud. The VPN connection was working fine but recently started experiencing intermittent connectivity issues. You are tasked with troubleshooting this problem. Which of the following actions should you take to identify and resolve the issue?
- A
Verify the shared secret on both ends of the VPN tunnel.
- B
Check the MTU (Maximum Transmission Unit) size configuration on both ends of the VPN connection.
- C
Ensure that Cloud NAT is enabled for the VPC network where the VPN is configured.
- D
Analyze the logs in Cloud Logging for the VPN gateway to identify connection errors.
- E
Verify that the on-premises firewall allows UDP port 500 and 4500 traffic.
Show answer and explanation
Correct answers: A, B, D, E
Explanation
Troubleshooting a VPN connection requires systematically verifying the configurations on both ends of the tunnel and analyzing logs for errors. Common issues include mismatched shared secrets, MTU size mismatches, and firewall configuration errors. Cloud NAT is unrelated to site-to-site VPN functionality and does not affect VPN connectivity.
- A. Correct.
The shared secret is used for authentication between the VPN gateways. If it's mismatched or has changed recently, it can cause connectivity issues.
- B. Correct.
MTU size mismatches can result in packet fragmentation or dropped packets, leading to intermittent connectivity problems. It's crucial to verify the MTU configuration.
- C. Incorrect.
Cloud NAT is not required for site-to-site VPN. It is typically used for outbound internet access for private instances, making this option irrelevant to the problem.
- D. Correct.
Logs in Cloud Logging can provide valuable insights into connection errors, such as failed negotiations, authentication issues, or packet drops.
- E. Correct.
VPN traffic relies on UDP ports 500 (IKE) and 4500 (IPsec). If these ports are blocked on the on-premises firewall, the VPN connection can fail or become unstable.