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This is part 2 of vDS (vNetwork Distributed Switch), My Understanding.

How does vDS work?

What will your instructor tell you? “Please don’t consider vDS is a switch connecting to Hosts. vDS is just a template”  Well, that’s what you always heard from all your instructors. but template of what? The answer is vDS is template of HIDDEN vSwitch sitting on your local host. vDS(the template) is managed by vCenter(high level operation) and your local Host(low level operation). Let’s see a diagram.

From this diagram, you can see there are two hosts. Each host has hidden switch which received template (vDS) from vCenter. The local template will be updated every 5 minutes like what I mentioned in Part 1.

Now, let’s open this hidden switch and see what’s happening in there.

As you can see, the hidden switch has forwarding engine and teaming engine which will be configured and controlled by setting in vCenter. There are two IO filters (not just one) is to be used in VMSafe. So what VMSafe does is let third party software (for example, the Trend Micro)  build a VM appliance and be certified by VMWARE to prove it won’t do any damage. That special VM will use special API to monitor traffice (like firewall) or check virus. Meaning, if you want to use VMSafe product, you have to use vDS, meaning you have buy Enterprise Plus license! I guess that’s why VMSafe product is not popular.

ok. Back to vDS. Let’s make a small conclusion. vDS is also a vSS. But it’s hidden in the Host. This hidden vSS is using template made by vCenter and Local Host so you can control traffic and share switch data between hosts.

Few things you need to know about vDS

vDS is capable to do everything vSS can do because it’s basically a super (hidden) vSS. Once you assign a vmnic OR VMkernal, SC or VM to vDS, you won’t be able to use them in vSS. It’s same thing as vSS.

I won’t say there are not much point to use vDS but if you do want to use vDS, you would either use Cisco Nexus to replace vDS or you want to use VMSafe product. Or you have Enterprise Plus license and want to use host profiles.

vDS timeout issue

vDS is not as convenient as vSS which only connects to single Host. sometimes, it’s not easy to remove vDS switches or even switch physical nic to different vDS switches. If vDS believes a port is busy, vCenter won’t allow you to delete vDS or remove a host from it. By the default, vCenter automatically forces all “busy” ports on all distributed switches to time out every 24 hours.

You can make change on vpxd.cfg to make it as 10 minutes.

vpxd.conf is located at c:\documents and settings\all users\application data\VMware\VMware VirtualCenter\vpxd.cfg

In vpxd.cfg, add the line <vpxd><dvs><portReserveTimeout>10</portReserveTimeout></dvs></vpxd> and save the file.

Restart vCenter. The default timeout is now set to ten minutes.

After the port reservation has timed out, remove the vNetwork Distributed Switch or dvPort group.

Reset the default timout by removing the line you previous added to vpxd.cfg.

Restart vCenter.

Best Practise for vDS daily operation

If you run into problem with vDS, always start checking from vCenter->Networking level. Because it has general view to tell you all vDS details such as IP on each port group, PVLAN info and which VM or kernal ports it connects. Then, you should drill down to single host ->Configuration->Networking to add or remove objects. If you do have issue, try to remove all objects to another vDS and then, make your change.

For the rest of details, like PVLAN, blocking of individual ports, you can check this file to continue your journey of vDS.

http://vmware.com/files/pdf/vsphere-vnetwork-ds-migration-configuration-wp.pdf

Reference:

http://kb.vmware.com/1010913

http://vmware.com/files/pdf/vsphere-vnetwork-ds-migration-configuration-wp.pdf

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One Comment

  1. Good article on the Distributed Switch. A small comment: in the picture vds-io-filter.png there should be “vNICs” at the top and not “VMnics”, as the vmnic represents a physical port in a physical NIC.


3 Trackbacks/Pingbacks

  1. […] as well as extra functionality compared to standard vSwitches. A good summary can be found at GeekSilver’s blog. […]

  2. […] You can view the switch configuration on a host (both vSS and dvS) using esxcfg-vswitch -l. It won’t show the ‘hidden’ switches used under the hood by the vDS although you can read more about those in this useful article at RTFM or at Geeksilver’s blog. […]

  3. […] You can view the switch configuration on a host (both vSS and dvS) using esxcfg-vswitch -l. It won’t show the ‘hidden’ switches used under the hood by the vDS although you can read more about those in this useful article at RTFM or at Geeksilver’s blog. […]

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