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Short version: Why does Test-Connection report "A non-recoverable error occurred during a database lookup" for an offline host on a different subnet?

I'm using PowerShell to ping a remote host with the Test-Connection cmdlet:

$Computer = "COMPUTER01"
Test-Connection -ComputerName $Computer -Count 3

I receive the following error message:

System.Net.NetworkInformation.PingException: Testing connection to computer
'COMPUTER01' failed: A non-recoverable error occurred during a database
lookup ---> System.ComponentModel.Win32Exception: A non-recoverable error
occurred during a database lookup.

My DNS servers are all Windows AD Controllers running the DNS service. I am able to resolve the hostname to IP address using nslookup:

Name:    computer01.domain.com
Address:  192.168.2.153

The MS website says the following:

This is a nonrecoverable error. This indicates that some sort of nonrecoverable error occurred during a database lookup. This may be because the database files (for example, BSD-compatible HOSTS, SERVICES, or PROTOCOLS files) could not be found, or a DNS request was returned by the server with a severe error.

https://msdn.microsoft.com/en-us/library/windows/desktop/ms740668(v=vs.85).aspx

Question: What "database lookup" might be failing?

Troubleshooting pt. 1

I have tried to ping the same host, which also fails but with a more familiar message:

C:\> ping COMPUTER01

Pinging COMPUTER01.domain.com [192.168.2.153] with 32 bytes of data:
Reply from 192.168.0.220: Destination host unreachable.

Running tracert for the target IP address confirms this:

C:\> tracert -d 192.168.2.153

7    40 ms    40 ms    40 ms  192.168.0.220
8  192.168.0.220  reports: Destination host unreachable.

This message indicates one of two problems: either the local system has no route to the desired destination, or a remote router reports that it has no route to the destination...

If the message is "Reply From < IP address >: Destination Host Unreachable," then the routing problem occurred at a remote router, whose address is indicated by the "< IP address >" field. Use the appropriate utility or facility to check the IP routing table of the router assigned the IP address of < IP address >.

https://technet.microsoft.com/en-us/library/cc940095.aspx

Troubleshooting pt. 2

I had a look at the ICMP packets using WireShark. I can see that the response from this router is:

Type: 3 (Destination unreachable)
Code: 1 (Host unreachable)

Destination unreachable is generated by the host or its inbound gateway to inform the client that the destination is unreachable for some reason... Unreachable TCP ports notably respond with TCP RST rather than a Destination Unreachable type 3 as might be expected.

https://en.wikipedia.org/wiki/Internet_Control_Message_Protocol#Destination_unreachable

And finally

I also have separate/independent confirmation that the target host is known to be off the network, which explains why the router cannot "reach" the target. I am still wondering why the Test-Connection cmdlet threw what is (to me) such a misleading exception message.

Charlie Joynt
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  • I will have a look at the hosts file (unlikely to be the problem I think) and wonder about the cache. Thankfully (?) the problem is still happening so I can test some things... – Charlie Joynt May 26 '16 at 12:11

2 Answers2

2

Thanks for sharing. You made me look at the docs as I was having the same error.

It appears that this is a "feature" of Test-Connection; they appear to know about this as they provide a workaround.

The help for Test-Connection says if you want it to return only a boolean you should use the -Quiet switch when calling otherwise it tries to return an object. Here it is verbatim:

When you use the AsJob parameter, the cmdlet returns a job object. When you use the Quiet parameter, it returns a Boolean. Otherwise, this cmdlet returns a Win32_PingStatus object for each ping.

https://technet.microsoft.com/en-us/library/hh849808.aspx

So -Quiet it is for me rather than -ErrorAction SilentlyContinue.

Charlie Joynt
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sdjuan
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    Thanks. Useful work-around for this problem especially when I only need true|false for whether the host is ping-able. – Charlie Joynt Sep 19 '16 at 13:25
1

After the troubleshooting I have put in to this, my conclusion is simply that Test-Connection is returning a very unhelpful error message and/or misinterpreting the "Destination host unreachable" response being received from the router.

If anyone else is seeing this I would suggest running a tracert to confirm whether there is any device in the route which may be returning a response to the ping request.

If you have any way other than ping to determine if the host is online or not that will make a good sanity check and help you work out whether you can ignore these errors (using -ErrorAction) on the assumption that the host is offline:

$Computer = "COMPUTER01"

if(Test-Connection -ComputerName $Computer -Count 1 -ErrorAction SilentlyContinue) {
  "Online"
} else {
  "Offline"
}

As a side note, it seemed that the only difference between ping and Test-Connection was that the time-to-live (TTL) on the ICMP packet differed between ping (128) and Test-Connection (80). The latter cmdlet does include a -TimeToLive switch if that is important to anyone; it didn't make any difference in my testing.

Charlie Joynt
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