Voice VLAN

In Cumulus Linux, a voice VLAN is a VLAN dedicated to voice traffic on a switch port. However, the term can mean different things to different vendors.

Voice VLAN is part of a trunk port with 2 VLANs that comprises either:

  • Native VLAN, which carries both data and voice traffic
  • Voice VLAN, which carries the voice traffic, and a data or native VLAN, which carries the data traffic in a trunk port.

The voice traffic is an 802.1q-tagged packet with a VLAN ID (which may or may not be 0) and an 802.1p (3-bit layer 2 COS) with a specific value (typically 5 is assigned for voice traffic).

Data traffic is always untagged.

Cumulus Linux Voice VLAN Example

You can configure the topology above using the following NCLU commands. In this configuration:

  • swp1 data traffic traverses the bridge’s native VLAN and the voice traffic traverses VLAN 200
  • swp2 data traffic traverses VLAN 10 and the voice traffic traverses VLAN 100
  • swp3 data and voice traffic both traverse the bridge’s native VLAN

    cumulus@switch:~$ net add bridge bridge ports swp1-3
    cumulus@switch:~$ net add bridge bridge vids 1-1000
    cumulus@switch:~$ net add bridge bridge pvid 1
    cumulus@switch:~$ net add interface swp1 bridge voice-vlan 200
    cumulus@switch:~$ net add interface swp2 bridge voice-vlan 100 data-vlan 10
    cumulus@switch:~$ net add interface swp3 bridge voice-vlan 300
    cumulus@switch:~$ net pending
    cumulus@switch:~$ net commit
    

These commands create the following configuration snippet in the /etc/network/interfaces file:

auto swp1
iface swp1
    bridge-vids 200
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
 iface swp2
    bridge-pvid 10
    bridge-vids 100
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp3
iface swp3
    bridge-vids 300
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto bridge
iface bridge
   bridge-ports swp1 swp2 swp3
   bridge-pvid 1
   bridge-vids 1-1000
   bridge-vlan-aware yes

Configure LLDP

Configuring voice VLAN with NCLU does not configure lldpd in Cumulus Linux, so LLDP-MED does not provide data and voice VLAN information. You can configure LLDP-MED for each interface in a new file in /etc/lldp.d. In the following example, the file is called /etc/lldpd.d/voice_vlan.conf:

cumulus@switch:~$ sudo nano /etc/lldpd.d/voice_vlan.conf
configure ports swp1 med policy application voice tagged vlan 200 priority voice dscp 46
configure ports swp2 med policy application voice tagged vlan 100 priority voice dscp 46
configure ports swp3 med policy application voice tagged vlan 300 priority voice dscp 46

You can also use the lldpcli command to configure an LLDP-MED network policy. However, lldpcli commands do not persist across reboots of the switch.

Troubleshooting

The bridge-vids can be reviewed with the net show bridge vlan command:

cumulus@switch:~$ net show bridge vlan

Interface      VLAN  Flags
-----------  ------  ---------------------
swp1              1  PVID, Egress Untagged
                200

swp2             10  PVID, Egress Untagged
                200

swp3              1  PVID, Egress Untagged
                300

You can get MAC address information using the net show bridge macs command:

cumulus@switch:~$ net show bridge macs

VLAN      Master    Interface    MAC                   TunnelDest  State      Flags    LastSeen
--------  --------  -----------  -----------------  -------------  ---------  -------  ----------
untagged  bridge    bridge       08:00:27:d5:00:93                 permanent           00:13:54
untagged  bridge    swp1         08:00:27:6a:ad:da                 permanent           00:13:54
untagged  bridge    swp2         08:00:27:e3:0c:a7                 permanent           00:13:54
untagged  bridge    swp3         08:00:27:9e:98:86                 permanent           00:13:54

You can capture LLDP information by checking syslog or using tcpdump on an interface.

Caveats and Errata

  • A static voice VLAN configuration overwrites a switch port’s existing configuration.
  • Removing the bridge-vids or bridge-pvid configuration from a voice VLAN does not remove the VLAN from the bridge.