Attempting to configure backups on the SDDC Manager results in an error "Invalid parameter: Failed to establish SSH session to x.x.x.x as the algorithm negotiation fail. Refer to the admin guide for the list of supported algorithms for SDDC Manager"

Products

• VMware SDDC Manager

Issue/Introduction

On the SDDC Manager UI - under Administration, Backup, Site Settings - the backup configuration fails to save.

A red banner error is displayed -

Failed to establish SSH session to x.x.x.x as the algorithm negotiation fail. Refer to the admin guide for the list of supported algorithms for SDDC Manager

The error below is observed in the log file /var/log/vmware/vcf/operationsmanager/operationsmanager.log

YYYY-MM-DD-hhTmm:ss:ss.sss+0000 ERROR [vcf_om,xxxxxxxxxxxxxxxx,xxxx] [c.vmware.vcf.secure.ssh.SshExecuter,http-nio-127.0.0.1-7300-exec-8] ERROR MESSAGE Algorithm negotiation fail
YYYY-MM-DD-hhTmm:ss:ss.sss+0000 ERROR [vcf_om,xxxxxxxxxxxxxxxx,xxxx] [c.vmware.vcf.secure.ssh.SshExecuter,http-nio-127.0.0.1-7300-exec-8] Authentication negotiation failed for host x.x.x.x
com.jcraft.jsch.JSchException: Algorithm negotiation fail

Environment

VCF 9.0

Cause

The algorithms and ciphers for an SSH session being presented to the SDDC Manager by the target backup server do not satisfy the requirements of the SDDC Manager, thus the algorithm negotiation fails.

Resolution

Please refer to the link below for the list of algorithms and ciphers that need to be configured for SSH on the target backup server, in order for SDDC Manager to be able to successfully negotiate an SSH session with it.

https://techdocs.broadcom.com/us/en/vmware-cis/vcf/vcf-9-0-and-later/9-0/fleet-management/backup-and-restore-of-cloud-foundation/reconfigure-sftp-backups-for-sddc-manager-and-nsx-manager.html

Once the appropriate algorithms and ciphers for an SSH session have been configured on the target backup server, the issue is expected to be resolved.