How can I troubleshoot BGP connection issues over Direct Connect?

3 minute read

My Border Gateway Protocol (BGP) session doesn't establish a connection over the AWS Direct Connect link, or it's in an idle state.

Resolution

If your BGP session doesn't establish a connection or is in an idle state, then complete the following tasks.

Check the Direct Connect link status

To bring up the BGP session, the physical Direct Connect link must be up, and there must be connectivity between the BGP peer IP addresses. Connectivity between the BGP peer IP addresses must be on both your side and on the AWS side.

If the physical connection is down, or if there's no connectivity between the BGP peers, then troubleshoot the OSI or BGP configuration. For more information, see My virtual interface BGP status For Direct Connect is down in the AWS console. What should I do?

Review the configuration on your Direct Connect router

Configure the following with the downloaded Direct Connect configuration file from the Direct Connect console:

Local and remote BGP peers
Local and remote BGP Autonomous System Numbers (ASN)
BGP MD5 password

Verify that the Direct Connect router or any other device isn't blocking ingress or egress from TCP port 179 and other ephemeral ports.

Because external BGP (EBGP) multi-hop is turned off on the AWS end, BGP peers can't be more than one hop away from each other.
Note: For a public virtual interface, verify that the BGP peer IP addresses are within the CIDR range that AWS approved. If the BGP peer IP addresses aren't approved, then the BGP session can't be established. For more information, see AWS Direct Connect FAQs.

Debug packet captures

To perform additional troubleshooting, review the following logs from your router:

BGP and TCP debugs
BGP logs
Packet captures for traffic between the BGP peer IP addresses

Check the BGP session if it changes from established to idle state

For private Direct Connect virtual interfaces, review the number of routes that you advertise over the BGP session. If you advertise more than 100 routes over the BGP session, then the BGP session goes into an idle state. Summarize the routes so that the number of advertised routes is less than or equal to 100. Or, advertise a default route over the BGP session to AWS.

If you have more than 100 networks in your on-premises network, then you can advertise a default route over the BGP session to AWS. Summarize the routes so that the number of advertised routes is less than 100.