When creating a CNV guest VM, with primary interface based on UserDefinedNetwork + secondary multus interface (attached to a node bridge) - none of the interfaces is assigned and IP address.
NetworkManager-wait-online.service service also fails starting, which seems to be related.

OCP 4.18.0-ec.3
CNV 4.18.0 (4.18.0-ec.3) 
nmstate-2.2.33-1.el9_4.x86_64

100 %

1.
Create a linux-bridge interface on all worker nodes using a NodeNetworkConfigurationPolicy resource like the attached nncp-linux-bridge.yaml

2.
Create a NetworkattachmentDefinition for the created linux-bridge like the attached linux-bridge-nad.yaml

3.
Create a UserDefinedNetwork resource like the attached 1-namespace-udn.yaml

4.
Create a VM with primary interface attached to the UDN, and a secondary interface attached to the NAD you created, by applying the attached 12-vma-primary-udn-secondary-multus.yaml
Please also note that the networkData section in cloud-init includes IP specification for both interfaces - dynamic for the primary (eth0) and static for the secondary (eth1):

            ethernets:
              eth0:
                dhcp4: true
              eth1: 
                addresses:
                - 10.200.1.1/24

5.
Start the VM (virtctl start vm-mul-udn-a) and wait for it to complete.

6.
Access the VM's console and check the IP addresses of its interfaces:
$ virtctl console vm-mul-udn-a
Successfully connected to vm-mul-udn-a console. The escape sequence is ^]

[fedora@vm-mul-udn-a ~]$ ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host noprefixroute 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 02:7f:cf:00:00:0b brd ff:ff:ff:ff:ff:ff
    altname enp1s0
    inet6 fe80::7f:cfff:fe00:b/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 52:54:00:fc:9f:49 brd ff:ff:ff:ff:ff:ff
    altname enp2s0

<BUG> None of the interfaces has an IP assigned.

Dynamic IP address from the subnet which is detailed in the UDN (192.168.88.0/24) for eth0, and the static IP address that is specified in the VM spec (10.200.1.1) for eth1. 

NetworkManager-wait-online.service fails starting:

× NetworkManager-wait-online.service - Network Manager Wait Online
     Loaded: loaded (/usr/lib/systemd/system/NetworkManager-wait-online.service; enabled; preset: enabled)
    Drop-In: /usr/lib/systemd/system/service.d
             └─10-timeout-abort.conf
     Active: failed (Result: exit-code) since Mon 2024-11-11 08:45:00 UTC; 3min 41s ago
       Docs: man:NetworkManager-wait-online.service(8)
    Process: 824 ExecStart=/usr/bin/nm-online -s -q (code=exited, status=1/FAILURE)
   Main PID: 824 (code=exited, status=1/FAILURE)
        CPU: 54ms

Nov 11 08:44:00 vm-mul-udn-a systemd[1]: Starting NetworkManager-wait-online.service - Network Manager Wait Online...
Nov 11 08:45:00 vm-mul-udn-a systemd[1]: NetworkManager-wait-online.service: Main process exited, code=exited, status=1/FAILURE
Nov 11 08:45:00 vm-mul-udn-a systemd[1]: NetworkManager-wait-online.service: Failed with result 'exit-code'.
Nov 11 08:45:00 vm-mul-udn-a systemd[1]: Failed to start NetworkManager-wait-online.service - Network Manager Wait Online.

(The full NetworkManager logs from journalctl are also attached in NetworkManager-journalctl.log)