DHCP Offer not transferred to tap interface

[Mu5hu]

Hi all,

I am on my journey to migrate from ESXi to Proxmox and first VM I need to migrate is the firewall (In my case pfSense).
I created a VM with 2 VirtIO nics, one for the WAN which comes directly from the ONT of my ISP and one for the LAN network. For the WAN I have a separated physical NIC which I created a bridge on and attached this bridge to the VM, the only specific configuration I made is assigning a static MAC address.

The issue comes when I want to configure the WAN interface like before, my ISP asks for a DHCP configuration which is the same as before but in Proxmox it is not working.

First thing, I made a tcpdump on the tap interface through the shell of Proxmox and analyse it through Wireshark:

tcpdump -i tap101i0 -w tap_dump.pcap

And from this capture I can see DHCP Discover packets rightly formed, source MAC is the static one I configured in the network interface of the VM
But I got no DHCP Offer back ... That's why I didin't get any IP !

What is interesting is, if I do the same tcpdump but this time on the Network interface of Proxmox but not on the bridge:

tcpdump -i ens0p0 -w net_dump.pcap

This time, I see the DHCP Discovery but also a DHCP Offer !

I also packet mirror the link on my switch and the packets are effetively there sent by the ONT

So it seems the packet is not transferred from the network interface to the tap and through the router.
ONT <--(ok)--> Network Interface <--(ok)--> tap101i0 <--(ko)--> Router VM


Is there any configuration I have done wrong ?
I also tried with an E1000E nic on the VM instead of the VirtIO one, but with no success.

 

[TheRealSentinel]

Hi all,
I am on the very same issuelike @Mu5hu, but one year later and running version 9.

Each Linux VM, (do not tested with other propietary Redmon OS yet) is able to communicate with an static IP address but does not receive a DHCP OFFER.

While dumping any of the interfaces I see DHCP Discovery process exiting from the VM, traversing bridge, Bridge VLAN, Service VLAN, Bridge0, Bonding and real interface.

It records a place in the DHCP server, and it responds with an offering that travels back until it reaches the vlan bridge but the interface tap. VM also ignores the IP is being offered.

Seems to me that there is a discontinued Layer 2. Or a gap in the middle.

I tried with Esx imported VMs running Debian on versions 10, 11 and 12 and also brand new installs with debian 13.

No luck so far.

Thanks in advance for any tip!

Alfred