NetWorker: Unable to Create the Connection with 'portmapper'

Summary: Backups from the NetWorker Linux client are randomly failing due to communication failure between the NetWorker server and the client although there are no network restrictions between the client and the server. NetWorker rely on the TCP/IP protocol for communication between the client and the server and modifying some TCP kernel parameters on the server, or the client can affect NetWorker functionality. ...

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Symptoms

NetWorker Linux client fails to backup with the following error reported in the backup action logs: 
nsrjobd RPC error RPC client handle: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.
nsrjobd RPC error Unable to create the connection with 'portmapper' to host 'client_name' with address 'ip_address' at port number 7938.  
nsrjobd RPC critical Check whether the firewall is blocking the client ports on the host 'ip_address'.
The following TCP parameters have been enabled on the system in the /etc/sysctl.conf file. 
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_tw_recycle  = 1
Errors from NetWorker Server /nsr/logs/daemon.raw: 
nsrjobd RPC error Unable to create the connection with 'portmapper' to host 'client_name' with address 'ip_address' at port number 7938.
nsrexecd RPC error Unable to create the connection with 'portmapper' to host 'client_name' with address 'ip_address' at port number 7938. 
nsrd RPC error Unable to create the connection with 'portmapper' to host 'client_name' with address 'ip_address' at port number 7938.
nsrexecd RPC critical Check whether the firewall is blocking the client ports on the host 'ip_address'. 
nsrjobd RPC critical Check whether the firewall is blocking the client ports on the host 'ip_address'.
Errors from other commands:
  • From the server, the command nsrrpcinfo -p client_name is not always working.
    • The first run of the command communicates successfully with the client, but the second immediate run fails.
    • The command fails to communicate with the client if the backup is running from the client.
  • The following command from server to the client is not always working:
  • The first run of the command communicates successfully with the client, but the second immediate run fails.
nsrports -t client_name -p 7938

Cause

Enabling the following Linux kernel parameters leads to communication failure in NetWorker: 
net.ipv4.tcp_tw_reuse 
net.ipv4.tcp_tw_recycle 
The parameters affect the kernel handling for sockets in TIME_WAIT status.

Resolution

In the /etc/sysctl.conf file, set the following parameters.   
net.ipv4.tcp_tw_reuse = 0
net.ipv4.tcp_tw_recycle = 0
Where 1 (enabled) and 0 (disabled)
 
Note: Enabling these TCP parameters is not recommended and consultation with the Linux vendor before enabling them is recommended. 

Additional Information

The tcp_tw_reuse allows the host to reuse the TCP connection in TIME_WAIT status for a new connection, without waiting for the socket to be closed.

The parameter tcp_tw_recycle enables fast recycling of sockets in TIME_WAIT status. By default, the Linux Kernel waits for two minutes (2 x MSL) before closing sockets in TIME_WAIT status if not closed by the application.

Affected Products

NetWorker

Products

Support, Solutions
Article Properties
Article Number: 000081987
Article Type: Solution
Last Modified: 24 May 2024
Version:  6
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