Name is not a valid hostname

I just ran into the same problem myself, as a new user/admin of networker.  I wanted to add a laptop that previously only got a pool (variable) DHCP address, so I added it to the DHCP server to assign a static address.  I could access the host and see the tree of files to choose to backup, but then it would complain it wasn't a valid hostname.

This error was preposterous since it had clearly accessed the host via this very hostname!  How could it not be valid?

I poked around this for a while, looking for this error in the 7.6 errors guide (couldn't find it).  Finally I saw a reference to networker needing the reverse lookup to work as well.  While I thought I'd properly configured the reverse table, it turned out I edited the file from a previous network configuration, not the one I needed for the new setup.  Changing that file fixed the problem.

I encourage the networker Powers That Be to change this error to a more informative one, such as "IP address A.B.C.D does not map to ".  I'm sure there are other cases where " is not a valid hostname" is exactly the right message, but at least in my case, it was very misleading.

I got the same error. Full message:

"Unable to connect to host. Please check networker security settings. Unable to dtermine the name of 192.168.15.142. No such host is known."

(where 192.168.15.142 was the IP of the Networker Server machine.)

My setup

Networker 8 Server on CentOS Linux

Networker Client on Windows 7

Windows Server 2008 R2 for DNS services

My solution

1. Set up DNS names for both. Check that ping in terminal/command prompt works on both machines

2. Set up Reverse look-up zones on the DNS server. Check that it works by going in to each machine and running command nslookup

3. Restart the Networker Server machine (I got other errors before restarting, but after that it worked).

Hi Harry,

This is name resolution issue , and most probably as the previous replies mentioned it is reverse lookup issue, but i would like to add another recommendation which is deleting the nsr peer information from the client and server, Please follow the steps given below to delete the NSR peer information on NetWorker Server and on the Client.

1. At NetWorker server command line, go to the location /nsr/res
2. Type the command: 
   nsradmin -p nsrexec
   print type:nsr peer information; name:client_name
   delete
   y

   (specify the name of the client in the place of client_name) 

1. At the client command line, go to the location /nsr/res
2. Type the command:
   nsradmin -p nsrexec
   print type:nsr peer information
   delete
   y

This is an additional recommendation beside the naming resolution investigations that is needed specially the reverse lookup.

Hope this helps,

Ahmed Bahaa

Verify if DNS or hosts file has entries for that hostname. If yes then you have to flush NW's DNS cache by command "dbgcommand -p FlushDnsCache" or restart NW server. After that you should be able to create client.