VLAN Management
Voice VLAN
Cisco Small Business 300 Series Managed Switch Administration Guide 122
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In MAC addresses, the first three bytes contain a manufacturer ID, known as an
Organizationally Unique Identifier (OUI), and the last three bytes contain a unique
station ID. The classification of a packet from VoIP equipment or phones is based
on the OUI of the packet source MAC address.
Ports can be assigned to Voice VLAN as follows:
• Static—Assigned manually to the Voice VLAN (described in the
Configuring VLAN Interface Settings section).
• Dynamic—The port is identified as a candidate to join the Voice VLAN.
When a packet with a source OUI MAC address that identifies the remote
equipment as voice equipment is seen on the port, the port joins the Voice
VLAN as a tagged port. (This is configured by using the process described
in the Configuring VLAN Interface Settings section.) If the time since the
last telephony MAC address was aged out of the MAC address table
exceeds the Voice VLAN aging time, the port is removed from the Voice
VLAN. The aging time can be changed by using the procedure described in
the Configuring Voice VLAN Properties section.
The following network scenarios are supported for dynamic assignment:
• A phone is configured with the Voice VLAN ID, and always sends tagged
packets.
• A phone sends untagged packets to acquire its initial IP address. A
response from the local DHCP server directs the phone to use the Voice
VLAN ID. The phone then restarts a DHCP session on the Voice VLAN
(tagged).
• If the voice equipment supports the LLDP-MED protocol, the switch sends a
LLDP-MED network policy that tells the phone to how to send frames to the
switch (for example: tagged, and tagged with what VLAN).
Voice VLAN Options
You can perform the following operations with this feature:
• Enable or disable Voice VLAN as described in the Configuring Voice VLAN
Properties section.
• Create a new VLAN to serve as the Voice VLAN by using the Create VLAN
Page, or configure an existing VLAN as described in the Configuring Voice
VLAN Properties section.
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