252 Cisco LAN Switching Configuration Handbook
■ (Optional) Use an 802.1Q trunk with no voice VLAN:
(interface) switchport voice vlan dot1p
The IP Phone is instructed to use an 802.1Q trunk and the 802.1p CoS priority
field, but all voice frames are placed in the null VLAN (VLAN 0). Frames from
the phone’s data port are sent untagged (the native VLAN). This enables the
voice priority information to be propagated without requiring a separate voice
VLAN.
■ (Optional) Use an 802.1Q trunk with no VLAN information:
(interface) switchport voice vlan untagged
The IP Phone is instructed to send all voice frames untagged, over the native
VLAN. As a result, no 802.1Q encapsulation is used, and no 802.1p CoS priori-
ty information can be propagated.
■ (Optional) Don’t instruct the phone at all:
(interface) switchport voice vlan none
■ The switch will not provide the IP Phone with a VVID to use. This is the
default configuration. The phone will have no knowledge of a voice VLAN,
and both voice and data frames are sent to the switch port over the same
access VLAN.
3. (Optional) Optimize the switch port for an IP Phone.
Tip A switch can perform the actions of the following configuration steps with a single
command: switchport host at the interface configuration prompt.
Note that this command effectively disables trunking on the switch port; however, the
switch port and the IP Phone still use a special form of 802.1Q trunking regardless.
a. Turn off EtherChannel support:
(interface) no channel-group
Support for dynamic EtherChannel configuration using Port Aggregation
Protocol (PAgP) is disabled, saving about 10 seconds of port startup time. See
section “4-3: EtherChannel” in Chapter 4, “Layer 2 Interface Configuration,” for
more information.
b. Enable Spanning Tree PortFast:
(interface) spanning-tree portfast
The switch port is tuned for a faster STP startup time by bypassing the listening
and learning STP states. The port can be moved into the forwarding state
immediately. See section “7-3: STP Convergence Tuning” in Chapter 7, “Spanning
Tree Protocol (STP),” for more information.
To Next Page
Loading...
Need help?
General