VLAN Configuration to support IP Phone

Answered Question
May 25th, 2010
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Hi,

one method to configure the switch port to  support voice is:

#interface FastEthernet0/1

(config-if)#switchport mode access

(config-if)#switchport voice vlan dot1p

(config-if)#switchport access vlan 20

refering cisco documents the command  switchport voice vlan dot1p 

The command voice vlan dot1p,  Instructs the switch port to use 802. 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.  priority of 5.

Can I say that the PC connected to  this port will take IP address form vlan 20 and the IP phone will take  the IP from native valn with priority 5?

Correct Answer by Ganesh Hariharan about 7 years 4 weeks ago

Hi,

Thank you for your reply,


I knew that why we are using voice vlan and data vlan and I knew the QoS and the phone can mark its traffic, I am working in Voice field. I post this in R&S forum because All waht I need the behaviour of the switch using this command:


once I configure the switch like below:


switchportmode access

switchportvoice vlan dot1p


switchportaccess vlan 25


What is the VLAN assigned for IP phone and the PC that is connected to the switch?


In the previous configuration the Data Vlan should be VLAN 25 to be more accurate : VLAN ID = 25 and Priority = 0.


Now what about IP phone? if I checked the IP address of the phone it should be:


VLAN ID = 0 (Native Vlan) and Priority = 5 ( this is what I think and this is what exactly I need ?)


Hi,


You are right PC will be in data vlan 25 and ip phone traffic will be native vlan .



Hope to Help !!


Ganesh.H

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Ganesh Hariharan Wed, 05/26/2010 - 02:07
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Hi,

one method to configure the switch port to  support voice is:

#interface FastEthernet0/1

(config-if)#switchport mode access

(config-if)#switchport voice vlan dot1p

(config-if)#switchport access vlan 20

refering cisco documents the command  switchport voice vlan dot1p 

The command voice vlan dot1p,  Instructs the switch port to use 802. 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.  priority of 5.

Can I say that the PC connected to  this port will take IP address form vlan 20 and the IP phone will take  the IP from native valn with priority 5?


Hi,


With Dot1p configured  The IP phone traffic, use the 802.1p priority tags, to other traffic, use the local default vlan (vlan0) transponders.The configuration of Voice traffic must have a CoS applied to it to give priority over data, the layer 2 CoS is 802.1p which resides within the 802.1q header. Some devices are configured without 802.1q frame tagging for vlans, however without dot1q, you cannot have dot1p, so therefore if you configure access ports where the phone(voice) and pc(data) reside on the same vlan, with no explicit configuration for a voice vlan, the phone will tag the voice frame with dot1q and insert a vlan of zero telling the switch they are only using dot1p and that the frame belongs to the native vlan.



Hope to Help !!


Ganesh.H


Remeber to rate the helpful post

JustForVoice_2 Wed, 05/26/2010 - 04:29
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Thank you too much for your reply.


What I know the 802.1q is responsible to assign VLAN for traffic. in other words:


VLAN ID = 802.1q

802.1p = CoS value


( If I am wrong please correct me).


In my case the configuration will be as the following :


Voice Packet: VLAN ID = 0 and 802.1p = 5.

Data  Packet: VLAN ID = 20 and 802.1p = 0. (best effort)


Is it like this???

Ganesh Hariharan Wed, 05/26/2010 - 05:33
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Thank you too much for your reply.


What I know the 802.1q is responsible to assign VLAN for traffic. in other words:


VLAN ID = 802.1q

802.1p = CoS value


( If I am wrong please correct me).


In my case the configuration will be as the following :


Voice Packet: VLAN ID = 0 and 802.1p = 5.

Data  Packet: VLAN ID = 20 and 802.1p = 0. (best effort)


Is it like this???


Hi,


The phone can carry voice traffic in IEEE 802.1Q frames for a specified voice VLAN with a Layer 2 CoS value. It can use IEEE 802.1p priority tagging to give voice traffic a higher priority and forward all voice traffic through the native (access) VLAN.The IEEE 802.1p is an extension of the IEEE 802.1Q (VLANs tagging) standard and they work in tandem. The 802.1Q standard specifies a tag that appends to an Ethernet MAC frame. The VLAN tag has two parts: The VLAN ID (12-bit) and Prioritization (3-bit). The prioritization field was not defined and used in the 802.1Q VLAN standard. The 802.1P defines this prioritization field.


To configure a port to instruct the phone to give voice traffic a higher priority and to forward all traffic through the 802.1Q native VLAN -- we configure switchport voice vlan dot1p


Configuring Voice Ports to Carry Voice and Data Traffic on Different VLANs here VLAN 1 carries data traffic, and VLAN 2 carries voice traffic. In this configuration, we must connect all Cisco IP Phones and other voice-related devices to switch ports that belong to VLAN 2-- we configure switchport voice vlan vlan_num


Hope to Help !!


Ganesh.H

JustForVoice_2 Wed, 05/26/2010 - 08:09
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Thank you too much for your reply.


What I know the 802.1q is responsible to assign VLAN for traffic. in other words:


VLAN ID = 802.1q

802.1p = CoS value


( If I am wrong please correct me).


In my case the configuration will be as the following :


Voice Packet: VLAN ID = 0 and 802.1p = 5.

Data  Packet: VLAN ID = 20 and 802.1p = 0. (best effort)


Is it like this???


Hi,


The phone can carry voice traffic in IEEE 802.1Q frames for a specified voice VLAN with a Layer 2 CoS value. It can use IEEE 802.1p priority tagging to give voice traffic a higher priority and forward all voice traffic through the native (access) VLAN.The IEEE 802.1p is an extension of the IEEE 802.1Q (VLANs tagging) standard and they work in tandem. The 802.1Q standard specifies a tag that appends to an Ethernet MAC frame. The VLAN tag has two parts: The VLAN ID (12-bit) and Prioritization (3-bit). The prioritization field was not defined and used in the 802.1Q VLAN standard. The 802.1P defines this prioritization field.


To configure a port to instruct the phone to give voice traffic a higher priority and to forward all traffic through the 802.1Q native VLAN -- we configure switchport voice vlan dot1p


Configuring Voice Ports to Carry Voice and Data Traffic on Different VLANs here VLAN 1 carries data traffic, and VLAN 2 carries voice traffic. In this configuration, we must connect all Cisco IP Phones and other voice-related devices to switch ports that belong to VLAN 2-- we configure switchport voice vlan vlan_num


Hope to Help !!


Ganesh.H


Hi,

Thank you for your reply,


I knew that why we are using voice vlan and data vlan and I knew the QoS and the phone can mark its traffic, I am working in Voice field. I post this in R&S forum because All waht I need the behaviour of the switch using this command:


once I configure the switch like below:


switchportmode access

switchportvoice vlan dot1p


switchportaccess vlan 25


What is the VLAN assigned for IP phone and the PC that is connected to the switch?


In the previous configuration the Data Vlan should be VLAN 25 to be more accurate : VLAN ID = 25 and Priority = 0.


Now what about IP phone? if I checked the IP address of the phone it should be:


VLAN ID = 0 (Native Vlan) and Priority = 5 ( this is what I think and this is what exactly I need ?)

Correct Answer
Ganesh Hariharan Thu, 05/27/2010 - 01:18
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Hi,

Thank you for your reply,


I knew that why we are using voice vlan and data vlan and I knew the QoS and the phone can mark its traffic, I am working in Voice field. I post this in R&S forum because All waht I need the behaviour of the switch using this command:


once I configure the switch like below:


switchportmode access

switchportvoice vlan dot1p


switchportaccess vlan 25


What is the VLAN assigned for IP phone and the PC that is connected to the switch?


In the previous configuration the Data Vlan should be VLAN 25 to be more accurate : VLAN ID = 25 and Priority = 0.


Now what about IP phone? if I checked the IP address of the phone it should be:


VLAN ID = 0 (Native Vlan) and Priority = 5 ( this is what I think and this is what exactly I need ?)


Hi,


You are right PC will be in data vlan 25 and ip phone traffic will be native vlan .



Hope to Help !!


Ganesh.H

JustForVoice_2 Thu, 05/27/2010 - 01:27
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but I think the IP address of the phone will be from VLAN 25 but the traffic of the voice will be carry on Vlan 0 is it right?

Ganesh Hariharan Thu, 05/27/2010 - 01:37
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but I think the IP address of the phone will be from VLAN 25 but the traffic of the voice will be carry on Vlan 0 is it right?



You are right but tell me how is the ip phone is taking the ip address via DHCP or static ip address configured,if DHCP then it will be given a gateway also which will the vlan configured in your switch.


Hope to Help !!


Ganesh.H

JustForVoice_2 Thu, 05/27/2010 - 02:40
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the IP phone should take the IP address from DHCP. and for sure the gateway will be configure.


thank you...

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