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z An untagged packet carries no VLAN tag.
z A tagged packet carries the tag of a VLAN.
To set an IP address and a voice VLAN for an IP phone manually, just make sure that the voice VLAN ID
to be set is consistent with that of the switch and the NCP is reachable to the IP address to be set.
How Switch 4500 Series Switches Identify Voice Traffic
Switch 4500 series Ethernet switches determine whether a received packet is a voice packet by
checking its source MAC address against an organizationally unique identifier (OUI) list. If a match is
found, the packet is considered as a voice packet. Ports receiving packets of this type will be added to
the voice VLAN automatically for transmitting voice data.
You can configure OUI addresses for voice packets or specify to use the default OUI addresses.
An OUI address is a globally unique identifier assigned to a vendor by IEEE. You can determine which
vendor a device belongs to according to the OUI address which forms the first 24 bits of a MAC address.
Switch 4500 series Ethernet switches support OUI address mask configuration. You can adjust the
matching depth of MAC address by setting different OUI address masks.
The following table lists the five default OUI addresses on Switch 4500 series switches.
Table 1-1 Default OUI addresses pre-defined on the switch
Number OUI address Vendor
1 0003-6b00-0000 Cisco phones
2 000f-e200-0000 H3C Aolynk phones
3 00d0-1e00-0000 Pingtel phones
4 00e0-7500-0000 Polycom phones
5 00e0-bb00-0000 3Com phones
Setting the Voice Traffic Transmission Priority
In order to improve transmission quality of voice traffic, the switch by default re-marks the priority of the
traffic in the voice VLAN as follows:
z Set the CoS (802.1p) priority to 6.
z Set the DSCP value to 46.