SDN problem "error vmbr100"

[M1k3y]

I just created my first SDN on my (single) Proxmox Server.

The goal was to have manage various networks connected as VLANs to the host in a future Cluster Setup. The VLAN already existed as a tagged Network on all Ports and has a working DHCP and DNS Server (physical Router).

What I set up:

Linux Bridge on Host

• "vmbr100"
• Bridge ports: eno2 eno3 (previously unused, eno3 currently not connected)
• no IP settings
• not VLAN aware

SDN Zone on Datacenter

• "LocalAll"
• Type: VLAN
• Bridge: vmbr100
• other settings empty

VNet on Datacenter

• "DMZ"
• Zone: LocalAll
• Tag: 4
• not VLAN Aware

Subnet on Datacenter for "DMZ" VNet

• Subnet and Gateway set to Network
• no SNAT
• no DNS Zone Prefix

Applying the SDN settings gives me Status OK. However my "LocalAll" SDN is Status error. On the host view it says for the VNet "SDN" under Details "error vmbr100".

However when adding an interface with the Bridge "DMZ" to a VM and running a dhcp client, I succesfully get an IP issued by my router (router status shows the lease).

Please someone help me understand, what the problem might be and how I can fix it.

Config files on proxmox host (shortened to relevant sections and redacted/annotated where applicable):

/etc/network/interfaces

iface eno2 inet manual

iface eno3 inet manual

auto vmbr100
iface vmbr100 inet manual
    bridge-ports eno2 eno3
    bridge-stp off
    bridge-fd 0

source /etc/network/interfaces.d/*

/etc/network/interfaces.d/sdn

#version:15

auto DMZ
iface DMZ
    bridge_ports ln_DMZ
    bridge_stp off
    bridge_fd 0
    alias DMZ VLAN 4

auto ln_DMZ
iface ln_DMZ
    link-type veth
    veth-peer-name pr_DMZ

auto pr_DMZ
iface pr_DMZ
    link-type veth
    veth-peer-name ln_DMZ

auto vmbr100v4
iface vmbr100v4
    bridge_ports  eno3.4 eno2.4 pr_DMZ
    bridge_stp off
    bridge_fd 0

ip l

# physical interfaces of host

3: eno2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master vmbr100 state UP mode DEFAULT group default qlen 1000
    link/ether XX:XX:XX:XX:XX:01 brd ff:ff:ff:ff:ff:ff
    altname enp1s0f1
4: eno3: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq master vmbr100 state DOWN mode DEFAULT group default qlen 1000
    link/ether XX:XX:XX:XX:XX:02 brd ff:ff:ff:ff:ff:ff
    altname enp2s0f0

# linux bridge, defined on host

20: vmbr100: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    link/ether XX:XX:XX:XX:XX:01 brd ff:ff:ff:ff:ff:ff

# SDN interfaces and accompanying virtual/sub interfaces

22: DMZ: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    link/ether ae:30:a4:79:ed:a6 brd ff:ff:ff:ff:ff:ff
38: ln_DMZ@pr_DMZ: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master DMZ state UP mode DEFAULT group default qlen 1000
    link/ether ae:30:a4:79:ed:a6 brd ff:ff:ff:ff:ff:ff
39: pr_DMZ@ln_DMZ: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master vmbr100v4 state UP mode DEFAULT group default qlen 1000
    link/ether 5a:b1:b9:4d:61:47 brd ff:ff:ff:ff:ff:ff
40: eno2.4@eno2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master vmbr100v4 state UP mode DEFAULT group default qlen 1000
    link/ether XX:XX:XX:XX:XX:01 brd ff:ff:ff:ff:ff:ff
41: vmbr100v4: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    link/ether XX:XX:XX:XX:XX:01 brd ff:ff:ff:ff:ff:ff
42: eno3.4@eno3: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue master vmbr100v4 state LOWERLAYERDOWN mode DEFAULT group default qlen 1000
    link/ether XX:XX:XX:XX:XX:02 brd ff:ff:ff:ff:ff:ff

# Interfaces of VM for testing

43: tap103i1: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master fwbr103i1 state UNKNOWN mode DEFAULT group default qlen 1000
    link/ether e6:c0:0a:4b:aa:56 brd ff:ff:ff:ff:ff:ff
44: fwbr103i1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    link/ether 1a:51:06:ee:d2:30 brd ff:ff:ff:ff:ff:ff
45: fwpr103p1@fwln103i1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master DMZ state UP mode DEFAULT group default qlen 1000
    link/ether d2:35:97:b1:3f:05 brd ff:ff:ff:ff:ff:ff
46: fwln103i1@fwpr103p1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master fwbr103i1 state UP mode DEFAULT group default qlen 1000
    link/ether 1a:51:06:ee:d2:30 brd ff:ff:ff:ff:ff:ff