VCF 3.9.1 introduced Application Virtual Network (AVN). Application Virtual Networks (AVN) are software-defined overlay networks. AVN makes it easy to create use cases like mobility and disaster recovery for the vRealize Suite components in the management domain of a VMware Cloud Foundation deployment I will not get into more details on how it works and would rather redirect you to read the details on this blog post on Application Virtual Networks.
VMware Cloud Foundation installation with version 3.9.1 will require setting up AVN at deploy time. Even though this is made optional in the 4.x deployments, it is mandated to deploy in 3.9.1. It also has benefits highlighted above if used.
One of the requirements for setting up AVN is to configure BGP peering on the Top-of-the-Rack switch and add the details of the Autonomous System ID in the deployment sheet for the VCF Management domain bring up.
The 3.9.1 version currently only supports ASN ID values below 65535 (2 byte or 16-bit) and anything more than that will throw an error during validation on the Cloud Builder VM. This might not show as an issue on the deployment parameter sheet unless you have an ASN ID ending with 0s. If you have 0s, it will truncate the 0s as shown in the below screenshot. The second ID is actually 65001.62300 but you don’t see the 0s.
The error on the Cloud Builder VM will look like below.
This is a known issue and is documented in the KB Article which is not very easy to find. That’s exactly why I put this blog post together to help people who run into the same issue.
The workaround is to reach out to VMware GSS team to obtain a patch for the Cloud Builder VM and install it. This is mostly the issue with how the form accepts value and nothing to do with the way BGP is configured so the patch will enable the Cloud Builder accept the 32-bit ASN ID.
Hope this helps.