Using Voice VLAN on GS7xxTS
As VoIP becoming more and more popular, it added new requirements for layer2
switches to support IP telephony. Because the sound quality of an IP phone call can
deteriorate if the data is unevenly sent, switches use QoS to provide classification and
scheduling such that network traffic through the traffic are forwarded in a predictable
manner.
Netgear GS724TP/GS748TP Gigabit PoE Smart Switches support a new feature called
Voice VLAN. It allows administrator to easily set up a VLAN to isolate and prioritize
voice traffic.
How’s the Voice VLAN work?
Voice VLAN allows administrator to define a VLAN to be used specifically for voice
traffic. Administrator will create a VLAN and specify it as the Voice VLAN. A Cost of
Service (CoS) value is also assigned to the Voice VLAN. The CoS value based on IEEE
802.1P has a value from 0-7 where 7 is the highest priority. Packet belongs to the Voice
VLAN will receive the set CoS.
To use the Voice VLAN, user will enable Voice VLAN globally on the switch and on the
ports which are going to be connected to voice devices. Voice VLAN can be enabled
with 2 type of operational modes – Secure mode and Unsecure mode. The operating
modes determine how the switch will treat non-voice traffic going through a port
activated for Voice VLAN.
The GS7xxTP uses OUI (Organizationally Unique Identifier) to decide if a packet is
indeed a voice packet. An OUI basically is the first six octets of a MAC address. Since
each network equipment manufacturers have different MAC addresses assigned and
administered to them by IEEE, using the OUI, the switch can identify if a packet is sent
by a specified IP telephony equipment manufacturer. The GS7xxTP is pre-configured
with OUIs of several major IP Telephony equipment manufacturers. If the VoIP device
the user owned is not in the pre-configured OUIs, it can be added manually.
When a packet goes through a port that is enabled for voice VLAN, if the switch
determine that it is a voice packet, it will automatically added that port as a TAGGED
member of the voice VLAN. If the switch determined that it is not a voice packet, it will
either drop the packet if the Voice VLAN is configured with secured mode, or it will
forward the packet according to the packet’s VLAN tag if the Voice VLAN is configured
with unsecured mode.
.
Step by Step instruction on using the voice VLAN feature
DHCP Server
TM 24 PORT
10/100 Mbps Fast Ethernet Switch
100Mbps
1
12
Link FDX
Green = Rx/Tx, Yellow = Collision
100Mbps
13
24
13
Power
Green = Rx/Tx,Yellow = Collision
NETGEAR
MODELFS524
12
1
Bay Networks
Normal / Uplink
24
Netgear GS700TP
VoIP Phone
In our example, a VoIP phone is connected to port 8 of the GS724TP. A DHCP server is
connected to port 13 of the GS724TP. The VoIP phone receives its IP address from the
DHCP server. The VoIP phone has a MAC address of 00:04:0d:e7:01:19. Therefore, the
OUI for the VoIP phone will be 00:04:0d.
1. Create a normal 802.1Q VLAN using the standard procedure. From Switch>VLAN->Properties, click on the Add button. On the Add Properties screen,
enter the VLAN ID and a name for the voice VLAN. In our example, we create
VLAN2 as the voice VLAN.
Click Apply and VLAN 2 will be created.
2. For the port that is going to be connected to a VoIP phone, it does not need to be
manually added to the voice VLAN. However, if a port connected to a non-voice
device and need to communicate to the VoIP phone, it must be manually added to
the voice VLAN. Or an OUI must be created for that device. In our example, the
VoIP phone receive its IP addresses from the DHCP server, therefore, the port
connected to the DHCP server must be a member of the Voice VLAN. As a
result, we added port 13 as an “untagged” member of VLAN2. From the Switch>VLAN->Membership window, we select 2 from the VLAN ID pull-down menu
and select U under port 13. Click Apply.
In addition, the PVID (port VLAN ID) of port 13 must be set to 2. From the Switch>VLAN->Interface PVID Settings window, enter 2 as the PVID of Interface g13.
Click Apply.
3. Now Voice VLAN must be enabled globally for the switch. From the Switch>VLAN->Voice VLAN->Properties window, select Enable as the Voice VLAN
Status. Enter the VLAN ID of the voice VLAN in the Voice VLAN ID textbox.
For Class of Service, we select CoS value 6 in our example. Click Apply.
4. Next we enable Voice VLAN on the port that is connected to the VoIP phone.
From the Switch->VLAN->Voice VLAN->Port Setup window, for each port that
will be connected to a VoIP phone, click on the port number to open the Modify
Port Setup Window.
In the Modify Port Setup window, select Enable as Voice VLAN Mode. For our
example, we will select Unsecure as Voice VLAN Security mode. In secure mode,
non-voice traffic through the port will be dropped. In un-secure mode, non-voice
traffic through the port will still be forwarded according to the VLAN tag of the
traffic.
5. If the VoIP phone is not manufactured by one of the manufacturer in the default
OUI list, it needs to be added to the OUI list. The OUI is the first six octet of the
MAC address of the device. To add a new OUI, click on the Add button from the
Switch->VLAN->Voice VLAN->OUI window.
From the Switch->VLAN->Voice VLAN->OUI window, Enter the first six octet of
the VoIP phone’s MAC address in the format of aa:bb:cc and a description of the
device. Click Apply.
6. At this point, Voice VLAN is configured. In our example, when the VoIP phone
is connected to port 8, port 8 will be added automatically as a tagged member of
VLAN 2 and it will receive an IP address from the DHCP server. To confirm that,
go to the System->Address Table->Dynamic Addresses window. The VoIP
phone’s MAC address will appear under the Voice VLAN. In our example, the
VoIP phone with MAC address 00:04:0d:e7:01:19 now shown as a member of
VLAN 2.
From the Switch->VLAN->Voice VLAN->Port Setup window, ports enabled for
Voice VLAN and connected to the VoIP phone will be shown in Actived status. In
our example, port G8 now shown with status as Activated.
Troubleshooting
If the VoIP phone does not get added to the Voice VLAN automatically, check the
following:
1. Make sure the MAC address of the VoIP phone is in the OUI list. You can find
out the MAC address of the VoIP phone by looking at the MAC address table
under the port it is connected to.
2. Make sure the port is enabled for Voice VLAN.
3. If the port is enabled for Voice VLAN and the port’s Voice VLAN status is
shown as Activated but the VoIP phone is not showing as a member of the Voice
VLAN, make sure the VoIP phone support 802.1Q VLAN tagging. The phone
need to tag the voice packet with the Voice VLAN’s VLAN ID. The GS7xxTP
will automatically make the port connected to the VoIP phone a “TAGGED”
member of the Voice VLAN. However, if the packets generated from the VoIP
phone are untagged, the packet will still get assign the PVID of the port,
according to IEEE 802.1Q standard. To check if it is the case, change the PVID of
the port to the VLAN ID of the Voice VLAN. If the VoIP phone then shown
under the Voice VLAN, the VoIP phone is not tagging the packet with the Voice
VLAN ID, check with the VoIP phone manufacturer on how to configure VLAN
tagging on the phone.