How to bypass vCenter from DNS resolution

Products

• VMware vCenter Server

Issue/Introduction

This article will help in bypassing the DNS resolution for a vCenter Server when the DNS Server is not available.

Situations where this could apply:

• vCenter Services are not starting because DNS resolution is not working.
• Services are started, but the vCenter will be inaccessible.
• vCenter is accessible only via IP address but not through FQDN.

Environment

VMware vCenter Server 8.0.x
VMware vCenter Server 7.0.x
VMware vCenter Server 6.x

Resolution

*Note: Once DNS resolutions issues are resolved (example faulty DNS server), it is recommended to undo these changes.  Using this workaround long term could cause DNS resolution issues as VC will no longer be resolving its name via the designated DNS server.

1. Login to vCenter via Putty/SSH.
2. Back a backup of the dnsmasq.conf file
   
   cp /etc/dnsmasq.conf /etc/dnsmasq.conf.original
   
   
3. Edit the dnsmasq.conf file and add addn-hosts=/etc/dnsmasq.hosts to the end
   
   

   Example of edited dnsmasq.conf 

   listen-address=127.0.0.1

   bind-interfaces

   user=dnsmasq

   group=dnsmasq

   no-negcache

   no-hosts

   log-queries

   log-facility=/var/log/dnsmasq.log

   domain-needed

   dns-forward-max=150

   cache-size=8192

   neg-ttl=3600

   addn-hosts=/etc/dnsmasq.hosts


4. Create a file in /etc/ called dnsmasq.hosts

vi /etc/dnsmasq.hosts
5. Add entries in the following format:
   
   IP [TAB] VCFQDN [TAB] VCSHORTNAME

For example:
   
   10.10.10.10 vcenter.example.com vcenter
6. Save the file with :wq
7. Restart the dnsmasq service
   
   systemctl restart dnsmasq.service
   
   Note: It may also be necessary to restart all the vCenter services.

Additional Information

This method can also be used while updating the case of a vCenter PNID, instead of creating a temporary DNS record for the process.