VMware Cloud Community
phykell
Enthusiast
Enthusiast

Multiple VLANs Spanning a Layer 2 and Layer 3 Switch - VST/Trunking?

Hi,

I'm doing a cabinet move of my VMware infrastructure and I can't have any downtime so the aim is to move a host to the new cabinet and vMotion everything over.

  • The original cabinet has a few hosts and a Dell 28xx layer 2 switch.
  • The new cabinet has one host (moved from the original cabinet) and a Dell 62xx layer 3 switch.
  • My infrastructure has a large number of VLANs

Here's where it gets interesting: I have a cable running between the two switches and my host in the new cabinet can see my vCenter VM running on a host in the old cabinet just fine - vCenter running in a VM in the original cabinet can see the host. I was able to vMotion a test VM over to the new cabinet (and Storage vMotion as there's a new SAN in there) but for some reason, the VM can no longer access the network via its VLAN. If, however, I take the cable out of the single port that's connecting the host to the new Dell 62xx switch and plug directly between the host and the switch in the old cabinet, it works fine so it must be something to do with the new 62xx switch and the VLANs or perhaps it's just the fact that connecting the two switches together needs to be configured for trunking somehow?

So the issue is that if I plug my host into the 62xx switch which is then plugged into a 28xx switch which the other hosts (one running vCenter) are themselves plugged into, VMs can no longer access the network on the host on the 62xx switch.

Is this a VLAN/trunking issue and if so, how do I resolve it?

Thanks for looking Smiley Happy

Reply
0 Kudos
2 Replies
HeathReynolds
Enthusiast
Enthusiast

It does sound like a VLAN Trunking issue. You will need to make sure the ports connecting the new switch and the old switch are configured as trunk ports, and are passing all of the VLANs. You will also need to make sure the ports on the new switch facing the host are configured as trunk ports, and allow the appropriate VLANs.

Since you can connect the host to the old switch and it works that does a good job of eliminating the host vSwitch configuration.

My sometimes relevant blog on data center networking and virtualization : http://www.heathreynolds.com
Reply
0 Kudos
phykell
Enthusiast
Enthusiast

Hi,

Thanks for your reply - I'm going to try and get it working today. I haven't done any configuration on the Dell 62xx (in the new cabinet) yet and the Dell 28xx (in the original cabinet) should hopefully not require any changes because it's only a layer 2 switch. I do have the option of replacing the 62xx with a another 28xx - would that be a easier fix do you think? I was hoping I'd be able to just link the switches with a LAN cable and that would be enough.

Based on your reply I then found this link which sounds like a similar issue:

http://en.community.dell.com/support-forums/network-switches/f/866/p/19339535/19812846.aspx

...and it implies I have to create a trunk port on the 28xx as well as on the 62xx though on the 62xx it appears I also have to explicitly allow all VLANs - not so on the 28xx I'm guessing? I really want to avoid having to configure the 28xx because it's a production switch and there's no possibility of downtime. In fact, the whole reason I'm doing the cabinet move as I am is to avoid downtime so it's a bit of a killer if I have to reconfigure switches just to get a connection to my second cabinet.

Thanks again.

Reply
0 Kudos