Saturday, December 4, 2010

Voice VLAN

The voice VLAN feature is provided to separate voice traffic from data traffic and assign higher priority to voice traffic, thus decreasing voice transmission delay and jitter.
You can assign or remove a port to or from the voice VLAN manually or have the switch do that dynamically by configuring the automatic voice VLAN assignment mode on the port.
On a port configured with the automatic voice VLAN assignment mode, the switch automatically assigns the port to the voice VLAN when receiving a packet with the source MAC address matching a recognizable voice device vendor OUI. As soon as the port is assigned to the voice VLAN, an aging timer starts. If no recognizable voice traffic has been received before the timer expires, the port is removed from the voice VLAN.

Network Diagram

Figure 1 Network diagram for automatic voice VLAN assignment configuration

Networking and Configuration Requirements

As shown in Figure 1, PC is connected to GigabitEthernet 1/0/1 of Switch A through IP phone 1, and IP phone 2 is connected to GigabitEthernet 1/0/2 of Switch A. IP phone 1 sends out voice traffic with the tag of the voice VLAN, while IP phone 2 sends out voice traffic without any VLAN tag.
Configure the voice VLAN feature to satisfy the following requirements:
l          Configure VLAN 2 as the voice VLAN, and set the aging time of the voice VLAN to 100 minutes. Use VLAN 6 to transmit user service data.
l          GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2 can recognize voice traffic automatically. Service data from PC and voice traffic are assigned to different VLANs and then transmitted to the server and the voice gateway respectively through Switch B.

Configuration Example


#
vlan 1 to 2
#
vlan 6
#
interface GigabitEthernet1/0/1
 port link-type trunk
 port trunk permit vlan 1 6
 port trunk pvid vlan 6
 voice vlan enable
#
interface GigabitEthernet1/0/2
 port access vlan 2
 undo voice vlan mode auto
 voice vlan enable
#
 voice vlan aging 100
 voice vlan mac-address 000f-2200-0000 mask ffff-ff00-0000 description IP Phone2
 voice vlan mac-address 000f-e200-0000 mask ffff-ff00-0000 description IP Phone1
 voice vlan 2 enable

Configuration Guidelines

By default, the system maintains the OUI list shown in Table 1-1. You can remove or modify these pre-defined OUI addresses as needed.
No.
OUI Address
Vendor
1
0001-e300-0000
Siemens phones
2
0003-6b00-0000
Cisco phones
3
0004-0d00-0000
Avaya phones
4
00d0-1e00-0000
Pingtel phones
5
0060-b900-0000
Philips/NEC phones
6
00e0-7500-0000
Polycom phones
7
00e0-bb00-0000
3com phones

l          To use a VLAN as a protocol VLAN and the voice VLAN at the same time, ensure that the voice VLAN assignment mode on the port to be associated with the protocol VLAN is not automatic mode. In automatic mode, the port cannot be assigned to the voice VLAN manually and thus can cause your attempt to associate the protocol VLAN with the port to fail.
l          You cannot set the voice VLAN as the default VLAN on a port in automatic voice VLAN assignment mode.
l          The switch supports only one voice VLAN.
l          Only a static VLAN can be configured as the voice VLAN.
l          In the voice VLAN operating in security mode, the device allows only the packets whose source address matches a recognizable voice device vendor OUI to pass through. All other packets, including authentication packets such as 802.1x authentication packets, will be dropped. Therefore, you are discouraged to transmit both voice and data in the voice VLAN at the same time. If that is needed, disable the security mode of the voice VLAN first.

Multiple VLAN Registration Protocol (MVRP) (GVRP)


Multiple VLAN Registration Protocol (MVRP) formerly known as GARP VLAN Registration Protocol (GVRP) or Generic VLAN Registration Protocol is a standards-based Layer 2 network protocol, for automatic configuration of VLAN information on switches. It was defined in the 802.1ak amendment to 802.1Q-2005.

Network Diagram


Networking and Configuration Requirements

On the network as shown in Figure 1-1:
l          Configure all the involved Ethernet ports on the switches as trunk ports that carry the traffic of all VLANs.
l          Enable GVRP both globally and on all the ports on each switch.
l          Configure static VLAN 5 for Switch C, static VLAN 8 for Switch D, and static VLAN 5 and static VLAN 7 for Switch E. Switch A and Switch B are not configured with static VLANs.
l          Set the registration mode of GigabitEthernet 1/0/1 on Switch E to fixed, and display dynamic VLAN registration information of Switch A, Switch B, and Switch E.

Configuration Example

l          Configuration on SwitchA
#
 gvrp
#
interface GigabitEthernet1/0/1
 port link-type trunk
 port trunk permit vlan all
 gvrp
#
interface GigabitEthernet1/0/2
 port link-type trunk
 port trunk permit vlan all
 gvrp
#
interface GigabitEthernet1/0/3
 port link-type trunk
 port trunk permit vlan all
 gvrp                           
l          Configuration on SwitchB
 gvrp
#
interface GigabitEthernet1/0/1
 port link-type trunk
 port trunk permit vlan all
 gvrp
#
interface GigabitEthernet1/0/2
 port link-type trunk
 port trunk permit vlan all
 gvrp
l          Configuration on SwitchC
#
 gvrp
#
vlan 5
#
interface GigabitEthernet1/0/1
 port link-type trunk
 port trunk permit vlan all
 gvrp
l          Configuration on SwitchD
#
 gvrp
#
vlan 8
#
interface GigabitEthernet1/0/1
 port link-type trunk
 port trunk permit vlan all
 gvrp
l          Configuration on SwitchE
#
 gvrp
#
vlan 5
#
vlan 7
#
interface GigabitEthernet1/0/1
 port link-type trunk
 port trunk permit vlan all
 gvrp registration forbidden
 gvrp

Configuration Guidelines

l          On a GVRP-enabled trunk port, you must configure the port trunk permit vlan all command to ensure that the traffic of all dynamically registered VLANs can pass through. To prevent users of unauthorized VLANs from accessing restrictive resources from a GVRP-disabled port, you are discouraged to use the command on the port.
l          Before enabling GVRP on a port, enable GVRP globally first.
l          GVRP can only be configured on trunk ports. You cannot change the link type of a trunk port with GVRP enabled.
l          GVRP is mutually exclusive with the service loopback feature.
l          In an MSTP network, GVRP can run on only the common and internal spanning tree (CIST). In addition, blocked ports on the CIST cannot receive/send GVRP packets.

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