How to troubleshoot a down Connect Peer?

To troubleshoot a down Connect Peer in your AWS Cloud WAN setup, especially when using Tunnel-less connect, you can follow these steps:

1. Verify BGP configuration: Ensure that your BGP local Autonomous System Number (ASN) and Amazon's ASN are configured correctly on both sides of the connection.

2. Check peer IP addresses: Confirm that the peer IPs for both sides of the BGP peering session are configured correctly.

3. Examine MD5 authentication: If you're using MD5 authentication, verify that the key is configured correctly and matches exactly on both sides. Be careful to check for any extra spaces or characters.

4. Review prefix limits: Ensure you're not advertising more than the allowed number of prefixes. While the exact limit for Cloud WAN Connect peers isn't specified in the provided sources, it's a good practice to check this.

5. Firewall rules: You've already allowed TCP port 179, which is good. Also ensure that any high-numbered ephemeral TCP ports are not blocked, as these are necessary for BGP to establish a TCP connection between the peers.

6. Check BGP logs: If possible, examine the BGP logs on your third-party appliance for any errors or warning messages that might provide more insight into the issue.

7. Verify route propagation: If the BGP session appears to be up on the third-party appliance but down on the AWS side, check if routes are being properly advertised and propagated.

8. Use AWS support tools: While there isn't a direct way to debug the BGP session from the AWS side mentioned in the provided information, you may want to contact AWS Support for additional troubleshooting steps or to see if they can provide more detailed diagnostics from their end.

9. Consider using AWS networking tools: Although not specifically mentioned for Cloud WAN, tools like Reachability Analyzer might be helpful in identifying networking issues between your on-premises network and AWS.

If after going through these steps the issue persists, it would be advisable to open a case with AWS Support for further assistance, as they may have additional tools or insights to help diagnose the problem from the AWS side.
Sources
Troubleshooting AWS Direct Connect - AWS Direct Connect
Troubleshoot a VPC peering connection - Amazon Virtual Private Cloud

Hi,

You may want to read this documentation to debug the BGP aspects of your connection: https://docs.aws.amazon.com/vpn/latest/s2svpn/Generic_Troubleshooting.html

This KC article may also be useful: https://repost.aws/articles/ARIKYhXEYyQQqtO2ulKERrbw/bgp-negotiation-over-aws-site-to-site-vpn-and-direct-connect-troubleshooting-strategies-for-efficient-networking

Best,

Didier