Avamar VM Image Backup Fails with Error Message:"NBD_ERR_NETWORK_CONNECT"

• VM backups fail with the following error: 

2015-11-18 09:44:15 avvcbimage Info <16041>: VDDK:DISKLIB-LIB   : Failed to open 'vpxa-nfcssl://[<Datastore_Name>] <VM_Name>/<VM_Name>.vmdk@<esx_name>.com:902' with flags 0x1e NBD_ERR_NETWORK_CONNECT (2338). 
2015-11-18 09:44:15 avvcbimage Info <16041>: VDDK:NBD_ClientOpen: attempting to create connection to vpxa-nfc://[<Datastore_Name>] <VM_Name>/<VM_Name>.vmdk@<esx_name>:902
2015-11-18 09:44:15 avvcbimage Info <16041>: VDDK:CnxAuthdConnect: Returning false because CnxAuthdConnectTCP failed 2015-11-18 09:44:15 avvcbimage Info <16041>: VDDK:CnxConnectAuthd: Returning false because CnxAuthdConnect failed
2015-11-18 09:44:15 avvcbimage Info <16041>: VDDK:Cnx_Connect: Returning false because CnxConnectAuthd failed
2015-11-18 09:44:15 avvcbimage Info <16041>: VDDK:Cnx_Connect: Error message: Host address lookup for server esx-dc-ams003.avg.com failed: Name or service not known 2015-11-18 09:44:15 avvcbimage Warning <16041>: VDDK:[NFC ERROR] NfcNewAuthdConnectionEx: Failed to connect to peer. Error: Host address lookup for server esx-dc-ams003.avg.com failed: Name or service not known
2015-11-18 09:44:15 avvcbimage Info <16041>: VDDK:NBD_ClientOpen: Couldn't connect to esx-dc-ams003.avg.com:902 Host address lookup for server esx-dc-ams003.avg.com failed: Name or service not known
2015-11-18 09:44:15 avvcbimage Info <16041>: VDDK:DISKLIB-DSCPTR: : "vpxa-nfc://[<Datastore_Name>] <VM_Name>/<VM_Name>.vmdk@<esx_name>:902" : Failed to open NBD extent.
2015-11-18 09:44:15 avvcbimage Info <16041>: VDDK:DISKLIB-LINK  : "vpxa-nfc://[<Datastore_Name>] <VM_Name>/<VM_Name>.vmdk@<esx_name>:902" : failed to open (NBD_ERR_NETWORK_CONNECT). 
2015-11-18 09:44:15 avvcbimage Info <16041>: VDDK:DISKLIB-CHAIN : "vpxa-nfc://[<Datastore_Name>] <VM_Name>/<VM_Name>.vmdk@<esx_name>:902" : failed to open (NBD_ERR_NETWORK_CONNECT).
2015-11-18 09:44:15 avvcbimage Info <16041>: VDDK:DISKLIB-LIB   : Failed to open 'vpxa-nfc://[<Datastore_Name>] <VM_Name>/<VM_Name>.vmdk@<esx_name>:902' with flags 0x1e NBD_ERR_NETWORK_CONNECT (2338).
2015-11-18 09:44:15 avvcbimage Error <0000>: [IMG0008] Failed to connect to virtual disk [<Datastore_Name>] <VM_Name>/<VM_Name>.vmdk (13) (13) You do not have access rights to this file
2015-11-18 09:44:15 avvcbimage Info <19644>: Connecting virtual disk [san_storage_dc_ams_00_web] <VM_Name>/<VM_Name>.vmdk
2015-11-18 09:44:15 avvcbimage Error <0000>: [IMG0008] VixDiskLib_Open([<Datastore_Name>] <VM_Name>/<VM_Name>.vmdk) returned (13) You do not have access rights to this file
2015-11-18 09:44:15 avvcbimage Info <9772>: Starting graceful (staged) termination, VixDiskLib_Open attempt to connect to virtual disk failed (wrap-up stage)
2015-11-18 09:44:15 avvcbimage Info <16052>: Terminating backup of all remaining virtual disks

The proxy is connected to ESX on port 902 and it is attempting to connect to the VM disk more than one time, but it fails due to network  issue (such as packet drops) with the following error: 

2015-11-18 09:44:15 avvcbimage Info <16041>: VDDK:DISKLIB-LIB   : Failed to open 'vpxa-nfc://[<Datastore_Name>] <VM_Name>/<VM_Name>.vmdk@<esx_Name>:902' with flags 0x1e NBD_ERR_NETWORK_CONNECT (2338).

Workaround:

1. Host VMotion the Virtual Machine that failed to be backed up (known above as "VM_Name") to another ESX server.
2. Run an on-demand backup of the migrated Virtual Machine.
3. Once completed successfully, the customer should engage their network team to check why packets are dropping between the proxy (referred above as "Proxy_Name") and the ESX (referred to as "esx_name").

Alternative workaround:

Check the ESX server's record in DNS to see if the proxy used for this group backup can resolve this ESX host with the same record.

To do this:

1. Open a PuTTY to the proxy used for the backup (for example, Proxy_Name).
2. Run the nslookup <esx_FQN> command.
3. If the result is negative, ask the customer to modify the ESX record on the DNS or add each proxy /etc/hosts file with the correct ESX FQN and IP.