NetWorker NVP vProxy: VM backup fails with "Err: 5037-Cannot resolve IP address from Host DD_HOSTNAME_FAILOVER "

The NetWorker VMware Protection (NVP) integration is configured with the vProxy Appliance. The Virtual Machine (VM) image level backups are failing to open a session to the target Data Domain device. The backup session log shows:

YYYY/MM/DD HH:MM:SS ERROR:  [NW_BUILD] UUID:VM_MOREF:VM_NAME: ddp_connect_with_config() failed, Hostname: DD_HOSTNAME, Err: 5037-Cannot resolve IP address from Host DD_HOSTNAME_FAILOVER for ip family 0
YYYY/MM/DD HH:MM:SS ERROR:  [NW_BUILD] UUID:VM_MOREF:VM_NAME: Unable to open session to target device "DD_HOSTNAME".

This symptom can be caused due to:

• Required ports are blocked between the vProxy and the Data Domain: 

NVP vProxy: Troubleshooting Network Connectivity For Backup and Restore Operations

• DD Boost Interface Group (ifgroup) / Multipath / HA is enabled
  When DD Boost ifgroups or DD HA/failover are configured, the DD can advertise a logical/failover name for data connections. NetWorker (or the DD Boost library) uses that name for the data path rather than the base hostname.

• DD’s own "system/failover name" is set to the alias
  On the Data Domain, the configured system/failover name may be the alias that is being handed back to the client during session setup.

• DNS/hosts mismatch or IPv4/IPv6 mismatch
  The alias does not exist in DNS (forward and/or reverse)

Perform one of the following options:

1. Review the Data Domain's ifgroup, multipath, or HA settings to see if the _failover alias is being advertised instead of the base hostname. Consult with Data Domain support as needed.
2. Log in to the vProxy over SSH (admin) and confirm if the Data Domain is DNS resolvable. The Fully Qualified Domain Name (FQDN), shortname, and IP address should all respond correctly: 
   1. nslookup DataDomain_FQDN
   2. nslookup DataDomain_ShortName
   3. nslookup DataDomain_IPaddress

1. 1. If the Data Domain is not resolvable over DNS and/or the error is also showing DD_HOSTNAME_FAILOVER add a /etc/hosts file entry on the vProxy for the Data Domain:

10.0.0.10           DataDomain01.domain.com       DataDomain01      DataDomain01-failover.domain.com

Confirm that the vProxy can reach the Data Domain at the following ports, resolving any ports that fail to respond: 22, 111, 131, 161, 2049, 2052

• NVP vProxy: Troubleshooting Network Connectivity For Backup and Restore Operations
• NetWorker: How to use the DDPCONNCHK tool to test DD ddboost connectivity from NetWorker Hosts