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We have a 3-host VMWare vSphere v4.1 cluster that has a connection to an untagged network (let's call it 192.168.10.0) using two physical adapters, vmnic1 and vmnic2. Both are currently marked as "active". All three hosts have identical network configurations.

I need to migrate this network to a trunked connection, where 192.168.10.0 is in a VLAN instead of being untagged. My plan is to disable vmnic1, plug it into the new trunk port then re-enable vmnic1 in a new virtual switch with VLANs configured.

What I'm wondering is:

  • Can you unhook an (active) interface from a virtual switch without disrupting traffic?
  • Can the network configuration be inconsistent across a cluster (not using HA) without causing global problems?

Bonus points:

  • Through some kind of magic, is it be possible to connect the tagged interface to the same virtual switch as the current untagged interface, making for a smooth transition?

Edit: (from comment)

Followup question: If I reconfigure the existing virtual switch on one host to use tagged traffic, and then perform a vMotion to that host... Could that make for a smooth transition, right? (Ignoring temporary ARP issues)

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  • Please show the current vswitch configuration. Also, which specific build number of ESXi are your hosts on?
    – ewwhite
    Oct 21, 2014 at 10:06
  • Current config: i.imgur.com/Fr5zoIR.png The network in question is on vSwitch3.
    – Arkenklo
    Oct 21, 2014 at 10:47

1 Answer 1

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Can you unhook an (active) interface from a virtual switch without disrupting traffic?

Yes, you can, assuming there's another uplink available to that vswitch.

Can the network configuration be inconsistent across a cluster (not using HA) without causing global problems?

Yes and no. You need to make sure your vmkernel interfaces are reachable. You can also make this transition one-by-one by offlining a host, modifying its config, testing connectivity and reenabling the host.

Through some kind of magic, is it be possible to connect the tagged interface to the same virtual switch as the current untagged interface, making for a smooth transition?

Not quite, the tagging is done at the portgroup level, so your priority should be to get the management network on the right VLAN (can also be done from the ESXi console). As long as your upstream switch ports have the right VLAN memberships, you'll be able to modify the portgroups and assign their VLAN IDs.

enter image description here

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  • Awesome, thanks! Followup question: If I reconfigure the existing virtual switch on one host to use tagged traffic, and then perform a vMotion to that host... Could that make for a smooth transition, right? (Ignoring temporary ARP issues)
    – Arkenklo
    Oct 21, 2014 at 10:43
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    If the required interfaces are all configured properly and management and vmotion IPs are reachable, then yes. That's why you can test this in maintenance mode.
    – ewwhite
    Oct 21, 2014 at 12:18

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