Article ID:5734
Introduction
The Voice Virtual Local Area Network (VLAN) is used when traffic from Voice over Internet Protocol (VoIP) equipment is assigned to a specific VLAN that is made up of voice devices such as IP phones, Voice over Internet Protocol (VoIP) endpoints, and voice systems. The switch can automatically detect and add port members to the Voice VLAN, and assign the configured Quality of Service (QoS) to packets from the Voice VLAN. If the voice devices are in different Voice VLANs, IP routers are needed to provide communication.
The Voice VLAN feature permits the switch ports to carry voice traffic with Layer 3 IP precedence and Layer 2 class of service (CoS) values from an IP phone. Based on IEEE 802.1p CoS, the switch supports QoS which uses classification and scheduling to send network traffic from the switch. You can configure the Cisco IP phone to forward traffic with an IEEE 802.1p priority, and configure the switch to trust or override the traffic priority assigned by an IP phone.
Configuring Voice VLANs ensures that the VoIP devices will not have to contend directly with the broadcasts, data, and other traffic from other VLANs which could cause delays when delivering the traffic. Voice VLANs make the network configuration simple by marking the packets for QoS and which are assigned higher priority.
In the scenario below, the ports on the switch that are connected to the IP Phones are configured with Voice VLAN settings.
The switch supports two dynamic Voice VLAN modes: Telephony Organization Unique Identifier (OUI) mode and Auto Voice VLAN mode. The two modes affect how Voice VLAN and/or Voice VLAN port memberships are configured. The two modes are mutually exclusive to each other.
- Telephony OUI — In Telephony OUI mode, the Voice VLAN must be a manually-configured VLAN, and cannot be the default VLAN. When the device is in Telephony OUI mode and a port is manually configured as a candidate to join the Voice VLAN, the device dynamically adds the port to the Voice VLAN if it receives a packet with a source MAC address matching to one of the configured telephony OUIs. An OUI is the first three bytes of an Ethernet MAC address.
- Auto Voice VLAN — In Auto Voice VLAN mode, the Voice VLAN can be either the default Voice VLAN, manually configured, or learned from external devices such as UC3xx or UC5xx, and from switches that advertise Voice VLAN in Cisco Discovery Protocol (CDP) or Voice Service Discovery Protocol (VSDP). VSDP is a Cisco-defined protocol for voice service discovery. Unlike Telephony OUI mode that detects voice devices based on telephony OUI, Auto Voice VLAN mode depends on Auto Smartport to dynamically add the ports to the Voice VLAN. If enabled, Auto Smartport adds a port to the Voice VLAN if it detects an attaching device to the port that advertises itself as a phone or media end points through CDP and/or LLDP-MED. To configure the Auto Voice VLAN settings on your switch through the CLI, click here.
Voice VLAN QoS
Voice VLAN can propagate the CoS/802.1p and Differentiated Services Code Point (DSCP) settings by using Link Layer Discovery Protocol-Media Endpoint Discovery (LLDP-MED) Network policies. The LLDP-MED is set by default to response with the Voice QoS setting if an appliance sends LLDP-MED packets. MED-supported devices must send their voice traffic with the same CoS/802.1p and DSCP values, as received with the LLDP-MED response.
You can disable the automatic update between Voice VLAN and LLDP-MED and use your own network policies.
Working with the OUI mode, the device can additionally configure the mapping and remarking (CoS/802.1p) of the voice traffic based on the OUI.
By default, all interfaces are CoS/802.1p trusted. The device applies the quality of service based on the CoS/802.1p value found in the voice stream. In Auto Voice VLAN, you can override the value of the voice streams using advanced QoS. For Telephony OUI voice streams, you can override the quality of service and optionally remark the 802.1p of the voice streams by specifying the desired CoS/802.1p values and using the remarking option under Telephony OUI.
Voice VLAN Constraints
The following constraints exist:
- Only one Voice VLAN is supported.
- A VLAN that is defined as a Voice VLAN cannot be removed.
In addition, the following constraints are applicable for Telephony OUI:
- The Voice VLAN cannot be Smartport-enabled.
- The Voice VLAN cannot support Dynamic VLAN Assignment (DVA).
- The Voice VLAN cannot be the Guest VLAN if the Voice VLAN mode is OUI. If the Voice VLAN mode is Auto, then the Voice VLAN can be the Guest VLAN.
- The Voice VLAN QoS decision has priority over any other QoS decision, except for the Policy or ACL QoS decision.
- A new VLAN ID can be configured for the Voice VLAN only if the current Voice VLAN does not have candidate ports.
- The interface VLAN of a candidate port must be in General or Trunk mode.
- The Voice VLAN QoS is applied to candidate ports that have joined the Voice VLAN, and to static ports.
- The voice flow is accepted if the MAC address can be learned by the Forwarding Database (FDB). If there is no free space in FDB, no action occurs.
Objective
To manually configure the Voice VLAN Telephone OUI settings on your switch, follow this workflow:
- Create a VLAN. For instructions on how to create VLANs using the Command Line Interface (CLI), click here.
- Configure Voice VLAN properties.
- Disable Auto Voice VLAN mode and enable Telephony OUI.
- (Optional) Configure Telephone OUI Table.
- Configure the Interface with Telephone OUI Settings.
This article provides instructions on how to configure Voice VLAN Telephony OUI Properties on a switch through the CLI.
Applicable Devices
- Sx350 Series
- SG350X Series
- Sx500 Series
- Sx550X Series
Software Version
- 2.3.0.130
Configure Voice VLAN Telephony OUI Properties
Configure Voice VLAN Properties
The default VLAN of the switch is VLAN 1 which cannot act as the Voice VLAN. However, if there is no other configured VLAN, VLAN 1 can be assigned to Voice VLAN.
Note: To know how to configure VLAN settings on your switch through the CLI, click here for instructions.
Step 1. Log in to the switch console. The default username and password is cisco. If you have configured a new username or password, which is highly recommended, enter those credentials instead.
Note: To learn how to access an SMB switch CLI through SSH or Telnet, click here.
Note: The commands may vary depending on the exact model of your switch. In this example, the SG350X switch is accessed through Telnet.
Step 2. From the Privileged EXEC mode of the switch, enter the Global Configuration mode by entering the following:
Step 3. In the Global Configuration mode, enter the Interface Configuration context by entering the following:
SG350X(config)#voice vlan id [vlan-id]- vlan-id — Specifies the Voice VLAN. The range is from one up to 4094.
Note: In this example, Voice VLAN 40 is being configured.
Step 4. Press Y on your keyboard to continue.
Step 5. To specify a value of VPT (802.1p VLAN priority tag) that will be advertised by LLDP in the Network Policy TLV, enter the following:
SG350X(config)#voice vlan vpt [vpt-value]- vpt-value — The VPT value to be advertised. The range is from 0 to 7.
Step 6. Press Y on your keyboard to continue.
Step 7. To specify a value of DSCP that will be advertised by LLDP in the Network Policy TLV, enter the following:
SG350X(config)#voice vlan dscp [dscp-value]
Step 8. Press Y on your keyboard to continue.
Configure Telephony OUI Operational Settings
To configure the Telephony OUI Operational settings, take note of these guidelines:
- To change the administrative state from auto-enabled (or auto-triggered) to OUI-enabled, you must first set the administrative state to disabled.
- The administrative state cannot be set to OUI-enabled if the Auto SmartPort administrative state is enabled.
- The administrative state cannot be set to OUI-enabled if the Voice VLAN is the default VLAN (VLAN 1). For OUI-enabled mode, the Voice VLAN cannot be VLAN1.
Step 9. To change the administrative state from auto-enabled (or auto-triggered) to OUI-enabled, you must first set the administrative state to disabled by entering the following:
SG350X(config)#voice vlan state [disabled]- disabled — Disable Auto Voice Vlan or Telephony OUI.
Step 10. Press Y on your keyboard to continue.
Step 11. To enable Telephony OUI Voice VLAN, enter the following:
SG350X(config)#voice vlan state [oui-enabled]- oui-enabled — Voice VLAN is of type OUI.
Step 12. To set the OUI Voice VLAN CoS, enter the following:
SG350X(config)#voice vlan cos [cos-value] [remark]The options are:
- cos value — Specifies the Voice VLAN Class of Service value. The range is from 0 to 7.
- remark — (Optional) Specifies that the L2 user priority is remarked with the CoS value.
Note: The CoS queue to be designated to the voice traffic is like a buffer that filters the outbound traffic, and holds it until it can leave the switch through an outgoing port. The default value is five. In this example, the CoS value is set to 7 which is the highest priority.
Step 13. To set the OUI Voice VLAN aging timeout interval, enter the following:
SG350X(config)#voice vlan aging-timeout [minutes]- minutes — Specifies the Voice VLAN aging timeout interval in minutes. The range is from one to 43200.
Note: In this example, the aging timeout interval is set to 600 minutes or 10 hours.
Configure Telephone OUI Table Settings
Step 14. (Optional) To configure the voice OUI table, enter the following:
SG350X(config)#voice vlan oui-table {[add|remove]mac-address-prefix} [description]The options are:
- add mac-address-prefix — Adds the specified MAC address prefix to the Voice VLAN OUI table. The length is three bytes.
- remove mac-address-prefix — Removes the specified MAC prefix address from the Voice VLAN OUI table. The length is three bytes.
- description — (Optional) Adds the specified text as a description of the specified MAC address to the Voice VLAN OUI table. The length is from one up to 32 characters.
The default Voice VLAN OUI table is:
|
OUI |
Description |
|
00:01:e3 |
Siemens AG Phone |
|
00:03:6b |
Cisco Phone |
|
00:09:6e |
Avaya Phone |
|
00:0f:e2 |
Huawei-3COM Phone |
|
00:60:b9 |
NEC/Philips Phone |
|
00:d0:1e |
Pingtel Phone |
|
00:e0:75 |
Veritel Polycom Phone |
|
00:e0:bb |
3COM Phone |
Note: In this example, a SamplePhone with MAC address prefix 00:34:ab is added in the OUI table.
Configure Telephone OUI Interface Settings
To have a Voice VLAN work properly, the voice devices, such as Cisco phones and VoIP endpoints, must be assigned to the Voice VLAN where it sends and receives its voice traffic. Some of the possible scenarios are as follows:
- A phone/endpoint may be statically configured with the Voice VLAN.
- A phone/endpoint may obtain the Voice VLAN in the boot file it downloads from a TFTP server. A DHCP server may specify the boot file and the TFTP server when it assigns an IP address to the phone.
- A phone/endpoint may obtain the Voice VLAN information from CDP and LLDP-MED advertisements it receives from their neighbor voice systems and switches.
The device expects the attaching voice devices to send Voice VLAN, tagged packets. On ports where the Voice VLAN is also the native VLAN, Voice VLAN untagged packets are possible.
Step 15. Enter the interface context of the port that you want to configure by entering the following:
SG350X(config)#interface [interface-id]- interface-id — Specifies the interface that will join the Voice VLAN.
Note: In this example, port ge1/0/13 is entered.
Step 16. To enable OUI Voice VLAN configuration on an interface, enter the following:
SG350X(config-if)#voice vlan enable
Step 17. To choose the OUI Voice VLAN CoS mode, enter the following:
SG350X(config-if)#voice vlan cos mode [src | all]The QoS attributes can be assigned per port to the voice packets in one of the following modes:
- all — QoS values configured to the Voice VLAN are applied to all of the incoming frames that are received on the interface and are classified to the Voice VLAN.
- src — QoS values configured for the Voice VLAN are applied to any incoming frame that is classified to the Voice VLAN and contains an OUI in the source MAC address that matches a configured telephony OUI.
Note: In this example, all is entered.
Step 18. Enter the exit command to go back to the Global Configuration context:
SG350X(config-if)#exit
Step 19. Repeat steps 15 to 17 to configure more interfaces.
Note: In this example, the port ge1/0/25 is assigned to the Voice VLAN which QoS attributes are applied to packets with OUIs in the source MAC address.
Step 20. Enter the end command to go back to the Privileged EXEC mode:
SG350X(config-if)#end
You should now have successfully configured the Voice VLAN Telephony OUI settings on your switch.
Display Voice VLAN Settings
Step 1. To display the Voice VLAN status for all interfaces or for a specific interface if the Voice VLAN type is OUI, enter the following:
SG350X#show voice vlan type oui [interface-id | detailed]The options are:
- type oui — Common and OUI-voice-VLAN specific parameters are displayed.
- interface-id — (Optional) Specifies an Ethernet port ID.
- detailed — (Optional) Displays information for non-present ports in addition to present ports.
Note: In this example, the information on the OUI-enabled Voice VLAN is displayed.
Step 2. (Optional) To display the voice vlan local information about the Voice VLAN local configuration, enter the following:
SG350X#show voice vlan local
Step 3. (Optional) In the Privileged EXEC mode of the switch, save the configured settings to the startup configuration file by entering the following:
SG350X#copy running-config startup-config
Step 4. (Optional) Press Y for Yes or N for No on your keyboard once the Overwrite file [startup-config]… prompt appears.
You should now have displayed the Voice VLAN Telephony OUI configuration settings on your switch through the CLI.