VE 8.0.4: VM iPXE dhcp not working

TheNetStriker

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Aug 2, 2019
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I'm using the latest Proxmox VE 8.0.4 and I'm trying to get the iPXE network boot to work.

When I configure an VM with EFI bios everything works perfectly, but VM's with Seabios iPXE cannot get an DHCP address.

The VM's both use the same bridge network. (vmbr0)

I analyzed the network packets on my pfSense firewall and I found out that iPXE on the Seabios does not set the broadcast bit in the DHCP discover packet. Because of this the firewall does not send an broadcast packet back, but a unicast packet to the ip. (See attached screenshot)

As far as I understand the broadcast bit should be set until an IP is received and set on the interface, but for some reason iPXE does not set this bit on the first dhcp discover packet. (Or outgoing packets with this flag are blocked for some reason)

I also tried to set set an ip and netmask manually in iPXE and then the dhcp discover works.

Any idea what could cause this problem?

Edit:
The problem only occurs on my Mellanox ConnectX-3 network cards. I've also enabled SR-IOV on the card.
If I instead use one of the integrated ethernet ports of the server then dhcp works fine.
 

Attachments

  • DhcpDiscover.png
    DhcpDiscover.png
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Last edited:
I am having a similar problem. If I use software like FOG or iVentoy that installs an operating system through PXE then the VM has no IP address. I am using SeaBIOS and the VMs all have the default settings. I never had a problem with earlier versions of Proxmox in regards to PXE. I've been using FOG installed on a Debian VM in Proxmox for years. I decided to try out iVentoy today and that is what led me to realize there was a problem.

I am going to create an EFI VM, install an os, capture it with FOG, and see if I can push the captured image down to a new EFI VM just to see if there are any problems.
 

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