From: Sergey Golovanov (sergey.golovanov@iementor.com)
Date: Fri Jan 26 2007 - 01:08:25 ART
You don't really need trunk config at all. Voice vlan is enough. Example:
interface FastEthernet0/7
switchport mode access
switchport voice vlan 20
switchport access vlan 7
spanning-tree portfast
Originally when cisco came out with voice vlan configuration on Catalyst IOS you had to configure trunk mode and native vlan for DATA traffic, but you no longer have to.
The problem with mode trunk is that the switch will put every VLAN you have on the switch in FORWARDING mode on this interface. So if you have 20 vlans, and vlan 7 is data, vlan 20 is voice, all 20 vlans will be in forwarding state on this phone port, unless you explicitely configure "switchport trunk allowed 7,20". All broadcast traffic on all vlans will always be sent to the phone. Try to configure switchport mode trunk and then do "show spanning-tree interface fas0/7" - you will see every vlan in Forwarding State.
Now change it to "switchport mode access, switchport access vlan 7, switchport voice vlan 20" and do "show spanning-tree interface fas0/7" -> you are only going to see two vlans in forwarding mode. The switch is still tagging voice packets with vlan 20 and it expects to see voice packets coming in tagged with vlan 20.
--------------------------------------------------------------------
Sergey Golovanov, CCIEx5 (R&S/Security/Voice/Service Provider/Storage)
"Please, don't ask me for my ccie #, there are reasons why I can't release it"
ieMentor Instructor and Content Developer
sergey.golovanov@iementor.com
http://www.iementor.com
> -------Original Message-------
> From: Rocco R21 <roccor21@hotmail.com>
> Subject: 7960 VoIP phone switch port
> Sent: Jan 25 '07 22:24
>
> Configuring a 7960 w/PC. If the phone I want to set up will be using
> dot1q frames then is it better to set the trunk dynamic desirable or is
> it better to hard code it with switchport trunk encap dot1a? Here's what
> I have right now: mls qos!interface FastEthernet0/7
> switchport trunk native vlan 7
> switchport mode dynamic desirable
> switchport voice vlan 20
> mls qos trust device cisco-phone
> mls qos trust cos
> spanning-tree portfast
> !
>
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