MKS: Internal Error” when connecting to the virtual machine console

Thought let’s share my experience about MKS error here, this issue is commonly observed on ESXi 5.5 and 6.0 version. I was able to fix this error post following below steps:

1. Restart of the Management Agent
2. If  host has can’t fork error (normally this issue has been observed on HP server) then you can follow VMware’s recommendation as mentioned in below link.              https://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2085618                                                     
3. Verify ESXi firewall policy. Refer the below link.          https://kb.vmware.com/selfservice/search.do?cmd=displayKC&docType=kc&docTypeID=DTKB_1_1&externalId=2005284                                      

       These ports are mandatory:          

          22 - SSH (TCP)

         53 - DNS (TCP and UDP)

         80 - HTTP (TCP/UDP)

         902 - vCenter Server / VI Client - UDP for ESX/ESXi Heartbeat (UDP and TCP)

         903 - Remote Access to VM Console (TCP) 443 - Web Access (TCP)

         27000, 27010 - License Server (Valid for ESX/ESXi 3.x hosts only)

     Additionally, these ports are optional:

     123 - NTP (UDP)

        161, 162 - SNMP (UDP)

        88 - Kerberos (UDP and TCP)

        464 - Active Directory (TCP and UDP)

        3260 - Software iSCSI (TCP)

  4. Open a command prompt on the vSphere Client machine and run these commands:

      Ipconfig /flushdns

      Ipconfig /registerdns

  5. Ensure that the VMware ESXi/ESX host has enough disk space in /var and other  required partitions

  6. Check if your host is resolving FQDN. If not, please solve FQDN issue.

  7. Solve DNS issues on ESXI and vCenter

  8. Uncheck security setting on ESXI host.

      Go to Config > Security > host

      Uncheck the Config.Defaults.security.host.ruissl

   9. If you are using ESXi 6.0 then it’s a known issue:

   To resolve this issue in ESXi 6.0, use one of these options:

• Power off and Power on the virtual machine.
• Migrate the virtual machine to another ESXi host using vMotion.
• Suspend and then resume the virtual machine.

       Refer below article for more details.

https://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2116542

Note: - VMware is releasing ESXi 6.0 U2 after  15th March to fix MKS error and other known issues on ESXI 6.0.