Google Professional Cloud Network Engineer Question 749
Select 3Google Cloud PlatformYou have configured a Cloud Router to establish BGP peering with an on-premises router. However, the BGP session remains in the 'CONNECT' state and never transitions to 'ESTABLISHED'. Which of the following steps should you take to resolve the issue?
- A
Verify that the on-premises router's IP address matches the configured BGP peer IP address on the Cloud Router.
- B
Ensure that the Cloud Router's advertised routes match the IP ranges the on-premises router is expecting.
- C
Check the firewall rules to ensure that TCP port 179 is open between the Cloud Router and the on-premises router.
- D
Verify that the BGP ASN configured on the Cloud Router matches the ASN expected by the on-premises router.
- E
Restart the Cloud Router to force a re-establishment of the BGP session.
Show answer and explanation
Correct answers: A, C, D
Explanation
When troubleshooting BGP peering issues, it is important to verify that the configuration on both ends is correct. This includes ensuring that the IP addresses and ASNs match, and that the required network traffic (e.g., TCP port 179) is allowed by firewall rules. Route advertisement mismatches and restarting the Cloud Router are not relevant to the transition of the BGP session from 'CONNECT' to 'ESTABLISHED'.
- A. Correct.
This is correct. For the BGP session to establish, the IP address of the on-premises router must match the BGP peer IP address configured on the Cloud Router.
- B. Incorrect.
This is incorrect. While route advertisement mismatches can cause routing issues, they do not prevent the BGP session from transitioning to the 'ESTABLISHED' state.
- C. Correct.
This is correct. BGP uses TCP port 179 for communication, and if this port is blocked by a firewall, the session cannot establish.
- D. Correct.
This is correct. A mismatch in BGP ASNs will prevent the BGP session from being established.
- E. Incorrect.
This is incorrect. Restarting the Cloud Router is not required for BGP configuration changes to take effect, and it is not a standard troubleshooting step for this issue.