I am trying to make sense of the different voice vlan options...
"switchport voice vlan {vlan-id | dot1p | untagged | none}"
The vlan-id option is used to specify a specific VLAN to use for voice traffic. Data traffic remains in native vlan. Uses 802.1p for Voice QoS.
The dot1p option is similar to the vlan-id option except it uses VLAN 0 for voice traffic. Data traffic remains in native vlan. Uses 802.1p for Voice QOS.
The untagged option places the voice packets on the native vlan. However, it seems to form a special 802.1Q trunk just like the dot1p and vlan-id options. Not sure if it uses 802.1p for Voice QoS or if no Voice QoS is used.
The None option places the voice packets on the native vlan and no special 802.1q trunk is formed. I would assume that since there is no trunk there is no differentiation between the traffic and hence 802.1p cannot be used so there is no Voice QoS taking place.
Above is how I understand it. So my question is what is the difference between "untagged" and "none"?
Does Untagged actually use 802.1p for Voice QOS?
If Untagged does use 802.1p for Voice QoS then what is the difference between using dot1p and untagged? They would be the same except that Voice traffic would be on VLAN 0 instead of the native VLAN. However, what advantage is it if they both can carry QoS. I guess there would be some security gained from using VLAN 0.
I am trying to grasp what the real difference is and what the pros and cons are for each option. I am a beginner on this topic so any help would be appreciated.
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I appreciate the post but I don't see how it answers any of my questions. The command I listed in my question is not anywhere in the configuration and you didn't explain any of the options I have listed above.
I am trying to understand the specific command and options. If your configuration answers them please elaborate as I am not seeing the connection nor do I know how your production network is setup.
on cisco catalyst switches (at least the ones I've worked with, the main difference is in CoS tagging. you can have untagged still honor CoS values but "none" just classifies all the traffic as the same, so you need to consider here whether all your voice is best effort or whether you should at least be respecting the CoS markings coming from the phone. In some cases, say you have a SIP trunk and your ISP won't honor QoS marking, then it doesn't matter how you classify your own traffic internally because your bottleneck is still going to be the WAN, so might as well ignore the markings and just make it all best effort. So the main difference is that the "untagged' traffic will still at least look at the other values, even if it doesn't remark and re-prioritize
They config I posted it for a VoIP on its own tagged vlan. All ports on my switch are trunks, the native port run the workstations. When the phone boots it gets it config and reboots, taggs it packets and runs on the tagged vlan. Then I traffic shape the trunk giving priority to the voice packets. But like mentioned above if you are using a hosted service or if you VoIP server is across a WAN link and you want to traffic shape you need to have a MPLS connection.
rpalmeira22,
You answered part of my question....what the difference between untagged and none was. However, since my guess that untagged might carry the QOS data then what is the difference between untagged and dot1p options? What advantage would you have using one or the other....dot1p uses VLAN 0 by default and untagged just uses the native vlan...seems to be the same difference to me. Is there any advantage either way other than just being different?
sorry, not really sure where to go with this line of questioning. It's not so much that there's an "advantage" one way or the other, if you have existing infrastructure that doesn't support .1p then you can't use it. As far as I know, the "untagged" setting does not use .1p but I will try to verify that.
So I'm reading this as you asking which would be "better" and there really isn't a performance difference in terms of network perfornance between using one or the other, it's simply a matter of how you implement based upon whether your doing a fully new install, integrating with existing equipment that may or may not upport some of these standards. Use whatever is easiest for you to implemtn.
one more good link to read: http://www.ciscopress.com/
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by: bhnmiPosted on 2007-12-17 at 11:02:24ID: 20486962
I would have trunks with the native VLAN being the data VLAN and use a tagged vlan for the voice, then use 802.1q to traffic shape. This is out of my router which is in production.
class-map match-all VOICE-PRIORITY
match access-group 150
!
!
policy-map POLICY1
class VOICE-PRIORITY
priority 512
class class-default
fair-queue
interface FastEthernet0/3/1
description Workstations and Printer/VoIP Trunk
switchport trunk native vlan 20
switchport trunk allowed vlan 1,20,40,1002-1005
switchport mode trunk
speed 100
service-policy output POLICY1
!
interface FastEthernet0/3/2
description Workstations and Printers/VoIP Trunk
switchport trunk native vlan 30
switchport trunk allowed vlan 1,30,40,1002-1005
switchport mode trunk
speed 100
service-policy output POLICY1
!
interface Vlan10
description Servers
ip address 192.168.1.2 255.255.255.0
ip nbar protocol-discovery
ip virtual-reassembly
ip route-cache flow
!
interface Vlan20
description Workstations and Printers
ip address 192.168.2.1 255.255.255.0
ip helper-address 192.168.1.19
ip nbar protocol-discovery
no ip next-hop-self eigrp 1
ip virtual-reassembly
ip route-cache flow
!
interface Vlan30
description Operations and Printers
ip address 192.168.3.1 255.255.255.0
ip helper-address 192.168.1.19
ip nbar protocol-discovery
no ip next-hop-self eigrp 1
ip virtual-reassembly
ip route-cache flow
!
interface Vlan40
description VoIP VLAN
ip address 192.168.4.1 255.255.255.0
ip helper-address 192.168.1.19
ip nbar protocol-discovery
ip virtual-reassembly
ip route-cache flow
!
access-list 150 permit udp any any range 6004 7039
access-list 150 permit udp any range 6004 7039 any
access-list 150 permit udp any any range 5000 5070
access-list 150 permit udp any range 5000 5070 any
access-list 150 permit udp any any eq 5567
access-list 150 permit udp any eq 5567 any
access-list 150 permit tcp any any eq 5566
access-list 150 permit tcp any eq 5566 any
access-list 150 permit tcp any any eq 5570
access-list 150 permit tcp any eq 5570 any
snmp-server community public RW
snmp-server ifindex persist