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March, 2010

Can’t Connect to a Virtual Machine’s Console..And It Isn’t DNS.

If you try to connect to a VM’s console from the VI Client and receive something similar to:

Unable to connect to the MKS: Failed to connect to server

Almost every time you see this it’s DNS. So check that first. Refer to this KB article too.

For me, I knew it wasn’t DNS as I did the normal tests and the KB article didn’t help. The problem started when I moved a customer’s vSphere cluster to a new management network. We created a new Service Console on each vSphere host in a new vSwitch on a new VLAN. Then we changed DNS to point to the new IP, removed the host from vCenter, and then added it back. Everything was fine, except for VM console. The fix for this is either to reboot the ESX host (preferably in maintenance mode!) or for a non-disruptive fix SSH in to the host’s console and type:

/etc/init.d/network restart

This refreshes the network configuration and allows you to connect again.  Easy!

5 thoughts on “Can’t Connect to a Virtual Machine’s Console..And It Isn’t DNS.”

  1. Oh Thank God…. After an eternity of “Check DNS” and “Check Firewall”, I finally ogt something that not only worked but makes sense..

    I owe you a beer…

  2. Thank you, Sir!

    You helped me a lot.

    Funny: I could connect without any problems from a host that was in the same IP-Subnet (10.1.1.x), but not from another Subnet (10.2.2.x).

    So I thougt long time, it cannot be the ESX (and I could ping in both directions).

    Great job!

  3. This might help too:

    To enable the proxy:
    a. Log in to the ESX host’s service console as root .
    b. Open /etc/vmware/config with a text editor.
    c. Add this line:

    vmauthd.server.alwaysProxy = “TRUE”

  4. Ran into this after migrating a host to a different subnet. I could only connect to VM consoles if I was on the same subnet as the host.

    This did the trick. Thanks!

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