VMware vSphere

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  • 1.  Subnet mask change

    Posted Oct 16, 2013 12:54 PM

    Hi,

    I've been through the previous postings on the forums and the knowledgebase but I can't find an exact answer for my question so here goes...

    We currently have a subnet mask of 255.255.0.0 on all hosts and guests.  For various reasons this needs to be changed to 255.255.255.0.  My question is: what is the correct order to make this change?  Do we start with the vCenter (it is virtualised) and then move on to hosts or should it be the other way round.  I'd like to do this non-disruptively if possible.

    Also when changing only the subnet mask will I still have to reconfigure things like Update Manager and single sign-on?

    Thanks,

    Steve



  • 2.  RE: Subnet mask change

    Posted Oct 16, 2013 03:10 PM

    I'd like to do this non-disruptively if possible.

    That would be quite not probable in case of virtual machines, who are residing and already have IPs.

    While coming to the VCs and the server itself, you can workaround the following:

    1. Have a new VC with the new subnet [This VC should not reside in the hosts which are to be changed]

    2. In the ESXi host, create a new vSwitch, and add an uplink. This uplink should be in the new IP subnet

    3. Once done, create a management portgroup in this newly created vSwitch.

    4. From the new VC, add the server to its inventory. When prompted for "Already in a VC", click Yes.

    5. Till now, the VMs are residing in a separate Virtual machine portgroup with the old uplink.

    6. Now create a new VM portgroup [Give a new name apart from the old one] to the new Vswitch and add the VMS to this portgroup. A lot of scripts are available. http://www.virtu-al.net/2009/10/19/powercli-mass-vm-portgroup-change/

    7. After this, the VMS will no longer work, unless their IPs are changed or in case of a DHCP server, the dhcpd process to be restarted or much better, rebooting all the VMS

    8. Now, from the first VC, remove the ESXi host and

    9. Login to the DCUI console of the ESXi host and give the new IP as management. And finally

    10. From the new VC, delete the first vSwitch portgroup containing the old management network

    And last but not the least, go for a coffee break once done :smileyhappy:



  • 3.  RE: Subnet mask change

    Posted Oct 16, 2013 03:11 PM

    The above steps can change a lot and be a little bit easier if you are using a DVSwitch



  • 4.  RE: Subnet mask change

    Posted Oct 16, 2013 03:22 PM

    Thanks for the reply.  That's pretty comprehensive.  We aren't using distributed switches.

    I was hoping there would be a more straight forward way of doing things.  I can cope with downtime for the guests - but not all at the same time.



  • 5.  RE: Subnet mask change

    Posted Oct 16, 2013 03:34 PM

    I can cope with downtime for the guests - but not all at the same time.

    Well, you can always add a second nic to the guests and connect the second of the nics to the newly created vSwitch having the new subnet. However, at last, your vms using network traffic will have to face downtime one way or another due to the change in IPs and the new nic taking over.

    Happy to help,

    _zXi_