AHV VM Networking Enhancements: VLAN Trunking

  • 25 May 2016
  • 5 replies

Userlevel 7
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Jason Burns talks about VLAN Trunking for Virtual Machines in AHV, which allows for more flexibility in bringing virtual networks to a virtual machine.

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5 replies

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Thanks for explaining that.:manhappy:
Userlevel 1
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Thanks for this I was looking at Vlan Tagging and this will work Great.
Userlevel 2
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Hi, why would you need multiple vlans on a single VM?
Userlevel 2
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There are a few reasons you might want to have multiple VLANs on a single VM. Usually it is because the VM does something networking related on many networks, but doesn't have the ability to add many network adapters. You might get stopped by the guest OS somewhere around 20-ish adapters.

  • Firewall VMs may want to filter traffic from one VLAN to another VLAN without adding a new virtual NIC.
  • Monitoring VMs may want to look at traffic on multiple VLANs or send traffic on multiple VLANs with a single vNIC.
  • Router VMs may want to route packets from one VLAN to another on a single virtual NIC.

In all of these cases we can bring multiple networks up to the VM all on a single vNIC.

For performance reasons I wouldn't recommend this approach in a high traffic environment. In production or high performance scenarios you'll have more available CPU for processing network packets on different VLANs with one vNIC per VLAN.

However, in the case where you want to be on 100 VLANs - you can't add that many NICs to an operating system and have it work - so you're back to VLAN trunking on a single vNIC.

Hope that helps explain the use case for this feature!
Userlevel 2
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Hi Jason, Thank you for the explanation, my environment is not that large, but your answer has given me food for thought and further investigation for possible future development.

Best regards