dot1p

Answered Question
Oct 2nd, 2008
User Badges:

Regarding

http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_25_sea/configuration/guide/swvoip.html


#switchport voice vlan {vlan-id | dot1p | none | untagged}


Configure how the Cisco IP Phone carries voice traffic:



•dot1p-Configure the Cisco IP Phone to use 802.1p priority tagging for voice traffic and to use the default native VLAN (VLAN 0) to carry all traffic. By default, the Cisco IP Phone forwards the voice traffic with an 802.1p priority of 5.




I did that -

SW1(config-if)#switchport voice vlan dot1p

% Voice VLAN does not exist. Creating vlan 0

SW1(config-if)#

19:40:29: %PM-2-VLAN_ADD: Failed to add VLAN 0 - VLAN not found.



Does it right behavior or not?

Correct Answer by Jon Marshall about 8 years 9 months ago

To be honest i don't know but from the preceding notes it does look like that. It would not be the first time that a document had an inconsistency.


I know i have seen configs where there was a voice vlan and it was not vlan 0, in fact i have never seen vlan 0 used in the way the documents suggest.


Unless somebody else can verify one way or another might be best to assume it is a typo.


Jon

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (2 ratings)
Loading.
rmv72 Fri, 10/03/2008 - 00:15
User Badges:

System image file is "flash:c3560-advipservicesk9-mz.122-25.SEE.bin"

Jon Marshall Fri, 10/03/2008 - 00:26
User Badges:
  • Super Blue, 32500 points or more
  • Hall of Fame,

    Founding Member

  • Cisco Designated VIP,

    2017 LAN, WAN

From the link you provided


"The voice VLAN should be present and active on the switch for the IP phone to correctly communicate on the voice VLAN. Use the show vlan privileged EXEC command to see if the VLAN is present (listed in the display). If the VLAN is not listed, see Chapter 13, "Configuring VLANs," for information on how to create the voice VLAN."


The command you are entering


switchport voice vlan dot1p


you are missing out the vlan id ie. the command should be


switchport voice vlan dot1p


As the above note states you also need to make sure the vlan already exists in the vlan database. If it doesn't then create it before trying to use it.


Jon


rmv72 Fri, 10/03/2008 - 00:49
User Badges:

Don't know who rated your post as Resolved but your answer didn't clear that problem...\


Do you offer to create VLAN 0?


VLAN list has range 1..4094


Jon Marshall Fri, 10/03/2008 - 01:01
User Badges:
  • Super Blue, 32500 points or more
  • Hall of Fame,

    Founding Member

  • Cisco Designated VIP,

    2017 LAN, WAN

It has nothing to do with vlan 0 because you can't use vlan 0. Pick an unused vlan eg vlan 20. Create this vlan in the vlan database


3560(config)# vlan 20

3560(config-vlan)# name voice-vlan


then you can use vlan 20 in your command ie.


switchport voice vlan 20 dot1p


Have you tried the above.


Jon

rmv72 Fri, 10/03/2008 - 01:15
User Badges:

Here part of guide-


This example shows how to configure a port connected to an IP phone to use the CoS value to classify ingress traffic, to use 802.1p priority tagging for voice traffic, and to use the default native VLAN (VLAN 0) to carry all traffic:


Switch# configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Switch(config)# interface gigabitethernet1/0/1

Switch(config-if)# mls qos trust cos

Switch(config-if)# switchport voice vlan dot1p

Switch(config-if)# end



There is not vlan number here...

Jon Marshall Fri, 10/03/2008 - 01:22
User Badges:
  • Super Blue, 32500 points or more
  • Hall of Fame,

    Founding Member

  • Cisco Designated VIP,

    2017 LAN, WAN

Okay sorry i didn't see that in the link you provided. The default native vlan is usually vlan 1 so i'm a bit confused. Vlan 0 is an internal vlan and is not normally available to be used.


The notes are contradictory because it says the available range is 1 - 4094 and then it talks about vlan 0 carrying the traffic.


I would create a dedicated vlan for voice traffic and try using that in the command as per previous post.


Jon

rmv72 Fri, 10/03/2008 - 01:37
User Badges:

Do you mean that they wrote it incorrect( forgot to add vlan-id)?

Correct Answer
Jon Marshall Fri, 10/03/2008 - 01:40
User Badges:
  • Super Blue, 32500 points or more
  • Hall of Fame,

    Founding Member

  • Cisco Designated VIP,

    2017 LAN, WAN

To be honest i don't know but from the preceding notes it does look like that. It would not be the first time that a document had an inconsistency.


I know i have seen configs where there was a voice vlan and it was not vlan 0, in fact i have never seen vlan 0 used in the way the documents suggest.


Unless somebody else can verify one way or another might be best to assume it is a typo.


Jon

Actions

This Discussion