How do vm's receive dhcp relay agent from MX when they are not physically connected to a switch port

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How do vm's receive dhcp relay agent from MX when they are not physically connected to a switch port

I have a MX100 configured with 2 vlans: vlan1 vlan10.

The dhcp server is on vlan1, and I have implemented dhcp relay agent with a different subnet on vlan10 in the MX100.

This will work for ports configured on the switches, but what about when people connect to the vm that do not connect to the physical port?  How can these vm's receive the new subnet?  Do I have to configure a Windows server dhcp relay agent instead of using the MX100 relay agent, and how will these vm's be on the vlan10?

 

thanks!

4 REPLIES 4
Brash
Head in the Cloud

I'm not quite sure where the VM's fit into your network.

But generally speaking, any VM on VLAN 10 will receive an IP from the DHCP server via the relay you setup. VM's on VLAN 1 will receive an IP directly from the DHCP server.

VM's on other VLAN's will not receive an IP lease and you will need to configure a DHCP relay for that VLAN somewhere in the network.

Lets say the esxi hosts connect physically to the Meraki Switches.  If I configure port5 to vlan10, then yes, whatever I plug in to port5 will receive an ip from the relay setup for vlan10.  But what about the vms that don't connect to a physical port?  How can I put them on vlan10 and receive the new subnet ip?  Would I have to have a Windows dhcp relay server (vm) on the new subnet?

RaphaelL
Kind of a big deal

No , you would not have to do any modification to the DHCP relays. The DHCP process* is a broadcast ( D-O-R-A ). As long as your broadcasts from your VM are reaching vlan10 , you should be fine. Without knowing anything more in your setup , you VM would only need to be bridged on vlan10.

Brash
Head in the Cloud

There's quite a few ways you could do this. A lot of it comes down to design choices. Eg.
 - Will the VM's and ESXi management use the same physical port on the server?
 - Will the VM's be on the same subnet and VLAN as ESXi Management or different?

Assuming your ESXi host and VM traffic will exit the same physical server port onto Meraki switch port 5, you can:
 - Configure Meraki port 5 as a trunk with Native VLAN 10, or Access VLAN 10
 - Leave the VM traffic untagged in ESXi

Or if you'd prefer to tag on ESXi, you can:
 - Configure Meraki port 5 as a trunk port with native vlan 1
 - Configure ESXi management to use VLAN 10
 - Configure your VM's to use VLAN 10 within ESXi

These are just a couple of ways you can configure the devices to have both ESXi and the VM's on VLAN 10 and receiving IP addresses, assuming that's what you're trying to do.

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