To Reproduce

• Load a config like this:

  network_config:
  - type: vlan
    device: nic5
    vlan_id: 136
  - type: vlan
    device: nic6
    vlan_id: 136
  

• No error raised:

  2025-10-22 06:38:22.160 DEBUG os_net_config.impl_nmstate.apply Updated the interfaces: vlan136
  2025-10-22 06:38:22.160 INFO os_net_config.config_provider nmstate: Successfully configured network_config
  2025-10-22 06:38:22.160 INFO os_net_config.main nmstate: Configured network_config successfully
  

• Note that VLAN only configured for nic6 (enp130s0f3):

  [root@compute-0 ~]# ip a sh vlan136
  27: vlan136@enp130s0f3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
      link/ether f8:f2:1e:03:a5:c6 brd ff:ff:ff:ff:ff:ff
  

Expected behavior
Raise and error in case same vlan_id configured inside type: vlan for different interfaces.

Bug impact
Little customer impact as it can be configured since it can be done another way (see Known workaround section).

Known workaround

• Load a config like this:

  network_config:
  - type: interface
    name: nic5.136
  - type: interface
    name: nic6.136
  

• As a result:

  [root@compute-0 ~]# ip -details l sh enp130s0f2.136
  28: enp130s0f2.136@enp130s0f2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
      link/ether f8:f2:1e:03:a5:c4 brd ff:ff:ff:ff:ff:ff promiscuity 0  allmulti 0 minmtu 0 maxmtu 65535 
      vlan protocol 802.1Q id 136 <REORDER_HDR> addrgenmode none numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 tso_max_size 65536 tso_max_segs 65535 gro_max_size 65536 gso_ipv4_max_size 65536 gro_ipv4_max_size 65536 
  
  [root@compute-0 ~]# ip -details l sh enp130s0f3.136
  29: enp130s0f3.136@enp130s0f3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
      link/ether f8:f2:1e:03:a5:c6 brd ff:ff:ff:ff:ff:ff promiscuity 0  allmulti 0 minmtu 0 maxmtu 65535 
      vlan protocol 802.1Q id 136 <REORDER_HDR> addrgenmode none numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 tso_max_size 65536 tso_max_segs 65535 gro_max_size 65536 gso_ipv4_max_size 65536 gro_ipv4_max_size 65536