[VCF] SDDC Manager communication to vRSLCM not working

In some cases, communication errors may occur between SDDC Manager and vRSLCM. These issues are typically caused by an SSH key mismatch rather than the UserPrivilegeSeperation or RhostsRSAAuthentication options.

SDDC Manager maintains multiple known_hosts files, similar to standard Linux distributions. In certain scenarios, the SSH host key of vRSLCM may change.

In my case, the vRSLCM SSH key changed after an upgrade from version 8.16 to 8.18. A few days after the upgrade, I noticed communication failures between SDDC Manager and vRSLCM. When attempting to connect to vRSLCM directly from SDDC Manager, an error indicated that the host key had changed. To resolve the issue, I manually compared the keys and re-imported the updated SSH key.

SDDC Manager primarily maintains two sets of known_hosts entries: one based on the FQDN and another based on the IP address.

FQDN known_hosts locations:

• /root/.ssh/known_hosts
• /etc/vmware/vcf/commonsvcs/known_hosts
• /home/vcf/.ssh/known_hosts
• /opt/vmware/vcf/commonsvcs/defaults/hosts/known_hosts

IP known_hosts locations:

• /root/.ssh/known_hosts
• /etc/vmware/vcf/commonsvcs/known_hosts
• /home/vcf/.ssh/known_hosts
• /opt/vmware/vcf/commonsvcs/defaults/hosts/known_hosts