From: Mark Snow (msnow@ipexpert.com)
Date: Tue Jan 08 2008 - 14:20:04 ARST
This configuration ...
>>
>> interface FastEthernet0/1
>> switchport access vlan 10
>> switchport mode access
>> switchport voice vlan 110
>> spanning-tree portfast
>> end
... automatically turns on Dot1Q header support for one single VLAN -
in this case being VLAN 110.
So this means that the Dot1Q header will be read and processed
normally (including the 802.1p bits) by the switch - however any
Dot1Q headers that came through without the VLAN ID of 110 - would be
ignored.
Also - on a 3560 switch - this statement 'spanning-tree portfast' is
redundant - since turning on 'switchport voice vlan xx' automatically
configures portfast to come on.
BTW, 'switchport voice vlan' does not only recognize the Dot1Q header
for the specified vlan for IP Phones - it will turn on recognition
support for that vlan for ANY device ;-)
HTH,
Mark Snow
CCIE #14073 (Voice, Security)
CCSI #31583
Senior Technical Instructor - IPexpert, Inc.
A Cisco Learning Partner - We Accept Learning Credits!
Telephone: +1.810.326.1444
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On Jan 8, 2008, at 4:29 AM, Joseph Saad wrote:
> As per DocCD, at
> http://www.cisco.com/univercd/cc/td/doc/product/lan/cat3560/12240se/scg/swvoip.htm
>
> *From the 3560 Config guide, Note *Voice VLAN is only supported on
> access
> ports and not on trunk ports, even though the configuration is
> allowed.
>
> It may work, but it is not supported to configure a voice VLAN on a
> trunk
> port.
>
> and
>
> http://www.cisco.com/en/US/docs/switches/lan/catalyst3550/software/release/12.2_25_see/configuration/guide/swvoip.html
> From the 3550 config guide,"You should configure voice VLAN on
> switch access
> ports."
>
> Regards,
> Joseph.
> On Jan 7, 2008 5:43 PM, WorkerBee <ciscobee@gmail.com> wrote:
>
>> Which one is more preferred? I have tested both and it works.
>> The only difference for F0/2, it runs extra STP VLAN 1 instance.
>>
>> It seems that F0/1 is less CPU intensive due to lack of DTP, STP
>> VLAN 1,
>> faster L2 convergence since it is static port.
>>
>> Any comments?
>>
>> Requirement
>> =========
>> Data : Vlan 10
>> Voice : Vlan 110
>>
>>
>> interface FastEthernet0/1
>> switchport access vlan 10
>> switchport mode access
>> switchport voice vlan 110
>> spanning-tree portfast
>> end
>>
>>
>> interface FastEthernet0/2
>> switchport trunk encapsulation dot1q
>> switchport trunk native vlan 10
>> switchport mode trunk
>> switchport voice vlan 110
>> spanning-tree portfast
>> end
>>
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