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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, or
  • 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 that has 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

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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 cumulus@switch:~$ net add interface swp1-3 stp bpduguard cumulus@switch:~$ net add interface swp1-3 stp portadminedge 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

Configuring 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.