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Webcast-Catalyst9k
New Member

qos command

Hi

I would like to know what is advantage of SWITCHPORT VOICE VLAN DOT1P , I mean what is diffrence between when I type this and when I do not ?

[I just know it sends voice and data over native vlan (vlan 0 ) ]

Thanks.

3 REPLIES

Re: qos command

Hi,

yes, but the voice traffic  should be tagged with 802.1p priority in this case.

See http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_25_sea/configuration/guide/swvoip.html#wp1050112

for details.

BR,

Milan

New Member

Re: qos command

Hi

Thank you so much for your reply , but based on the link again : switchport voice vlan vlan-id based on this command ip phone sends 802.1q priority of 5 .

and with SWITCHPORT VOICE VLAN vlan-id 802.1P ip phone also forwards traffic with an 802.1p pririty of 5.

So what is advantage using second command ?

Thanks.

Re: qos command

Hi,

IMHO, there is no advance.

In the first case, the switch will send instructions to the phone (via CDP) to use 802.1q header for voice traffic tagging it to VLAN x.

In the second case, the VLAN tag will be empty (zero), as 802.1p can't be used without the 802.1q header.

In both cases, the phone uses 802.1p priority 5 by default.

See also

http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_25_see/command/reference/cli3.html#wp1948866

and

http://www.cisco.com/en/US/tech/tk389/tk689/technologies_tech_note09186a0080094665.shtml#topic2

BR,

Milan

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