vmware data protection (VDP) ip/dns could not be resolved

“ANY” (*) DNS Query is used by VMware Data Protection (VDP)

After a VMware migration from version 4.5 to 5.5, I struck-up in the installation of VMware Data Protection (VDP) 6.1.1. The deployment of VDP appliance got succeeded. But while configuring the appliance through the web browser (link : https://vdp.example.com:8543/vdp-configure/), it return an error.

“IP/DNS could not be resolved. Please check the hostname, domain, and DNS values for forward and reverse lookup validation”


Here are some testing results and diagnosing methods which I used to find the root cause of the error. This may help someone to troubleshoot the the same error.

As it is a DNS error, the initial diagnosing is done with the Nslookup command. Verify both forward and reverse lookups are correct for both VCenter and VDP. At this stage (Network Settings) It checks only the DNS of VDP appliance.
Using following names and IPs to explain instead of the actual IP and Hostnames

Vcenter IP :
Vcenter FQDN : vcenter.example.com
VDP FQDN : vdp.example.com
DNS FQDN  : dns.example.com

As per the vmware-KB-2036396  it should ping and respond to the nslookup (default A record) from both Vcenter and VDP.

nslookup vdp.example.com
nslookup vcenter.example.com

nslookup vmware vdp

If it is not giving the output you may also check the following

Telnet to the DNS server and make sure that the service is accessible in the port 53 (“telnet 53” ). This will fail if both DNS server and VDP are in different network zones and not properly configured firewall rules.

In my case all the forward and reverse lookups were working fine and still getting the same error.

At this stage , I Just confirmed the names in “/etc/hosts” vdp.example.com vdp localhost.localdomain localhost

Make sure that your DNS server is listed in /etc/resolv.conf


Still getting the same DNS error. Now talked to vmware support and they instructed to check the above settings same as listed in the vmware-KB.And their second try was to re implement the older appliances. and we tested with VDP 6.1.1, 6.1, 5.8.1, and 5.8.

Appliance 5.8.X will show some SSL error, and will not open in most browsers without a patch as per Vmware ( known issue )


Fix script is in this Vmware-KB-2111900

VMware Data Protection web configure still showing the “IP/DNS could not be resolved” message when configuring the Network settings.

Now I run a network packet sniffer ( tcpdump ) in the VDP server. Tcpdump is inbuilt in almost all the linux distributions. VDP is build with SUSE Linux. It is better to work with a SSH client like putty instead of working from a vmware console.
The default root password of VPD appliance is “changeme”. However it will show an authentication error if we try ssh to the vdp.This is because SSH is disabled for root login by default .

How to enable ssh In VDP server

Open file “/etc/ssh/sshd_config” and find the line “PermitRootLogin yes” and uncomment it. now restart the ssh server with

"/etc/init.d/sshd restart"

Again BACK to the packet sniffer TCPdump to debug

Connect SSH to the VDP server and run following command to monitor only the DNS queries.

tcpdump -vvv -s 0 -l -n port 53

Now from another SSH session test a DNS request using Nslookup

nslookup vdp.example.com

Important portion of the response output

q: A? vdp.example.com. 1/0/0 vdp.example.com. A

Now run the VDP web configuration and apply Network settings to simulate the DNS error and check the request response in tcpdump
Request is initiated by vdp-configure/services/dns/dolookup web call

Important portion of the response output

q: ANY? vdp.example.com. 0/1/0 ns: example.com. SOA dns.example.com.

tcpdump DNS output

Here there is no information about the IP address. Noticed that VDP appliance webconfig is using a “ANY” meta query instead of normal A record check. In my case this is the reason for the DNS error.

Here my DNS server is running on a linux box with “unbound”. We have been using this for long time in my organization for the Internet and Intranet DNS needs. As per my understanding UNBOUND server is a single purpose DNS server. There is no code to support Dynamic DNS updates, or zone transfers, etc. As it is not able to respond to “ANY” query, I have to find a workaround. So I configured a different Linux server with BIND for Just to Answer the DNS requests from VDP Server.

Now the questions come up like, what is “ANY” record in DNS ? why it is used in this appliance ? why my DNS server is not responding for the “ANY” query. ?

“ANY” is a special DNS meta query. Instead of doing a single query like A / NS, “ANY” retrieves all the available records of a domain name.
This is one of the request which can get a biggest DNS reply from a DNS server. Even if it is named ANY It really look like ALL records. It is also known as ‘*’. This can also be used for Zone transfer between DNS servers. Users can easily get the entire DNS zone with one command.
It can also be used for a DNS Amplification DDoS Attack. That is why some of the DNS servers are not responding to “ANY” query.
Basic reason for adding the ANY to DNS had been to assist in debugging and testing, there is no real reason to check the DNS ANY query from an application.

How to query “ANY” or “*” using Nslookup / dig ?

dig ANY google.com @
nslookup -q=ANY google.com @

Also bear in mind that, As there is a limit in the UDP packet size, the largest DNS responses need a TCP connection instead of UDP connection to port 53. Make sure that the TCP and UDP for port 53 is opened in the firewalls.

About Albin Sebastian

I am a Technology Blogger, System Administrator by profession and webmaster by passion. Technology blogger, Active in Online and offline tech communities.

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