Voice VLAN Configuration

Posted on 2015-02-23
Last Modified: 2015-02-24
Some question while reading a CCNP article,

To select the voice VLAN mode that will be used.
Switch(config-if)# switchport voice vlan {vlan-id | dot1p | untagged | none}

Should I issue this on the Cisco IP phone (left hand side), or the Catalyst switch (right hand side) connecting the Cisco phone  ?

Under Cisco configuration, the interface shows trunk, access and voice. Does it only apply to Cisco phone as a normal catalyst switch can only be configured with either access or trunk port ?  Correct ?

Question by:AXISHK
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LVL 29

Expert Comment

by:Predrag Jovic
ID: 40625290
You should issue that command on switch.
There is a special config for attaching Cisco phone where both Voice and Data attached to the same port can be configured as access ports.

#switchport voice vlan 10
#switchport access vlan 20

The reason why this can be done for Cisco phone is cdp.
For using non Cisco phone trunk must be manually configured.

Cisco configuration examples and details.

Author Comment

ID: 40625532
From the book, "The voice an user PC ports always function as access-mode switch ports. The port that connects to upstream switch can operate as an 802.1Q trunk or access-mode (single VLAN) port."

Still can't get the idea exactly. Should the port be configured with Trunk as well so that two different VLANs can go back to the Catalyst switch ?

LVL 29

Expert Comment

by:Predrag Jovic
ID: 40625971
That sentence talk about phone. Phone has it's own switch inside of phone.
Port on phone that is connected to PC and port that is connected to phone (although you can't see that port) always are connected as access ports.
However, port that connects phone with switch can operate as access or trunk port.
Switch on Cisco phone will negotiate it's trunk configuration with upstream switch.
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Author Comment

ID: 40627171
To clarify my understanding,

From your first response, "You should issue that command on switch." Are you talking about the Catalyst switch, correct ? On Catalyst switch, the port (connecting to Cisco phone) will be configured as "switchport voice" and "switchport access". Whether the port on Catalyst switch will operate as "access" or "trunk" depends on the negotiation with Cisco phone, correct ?

No configure is needed for the switch inside the Cisco phone, and it will configure either as access (voice and data in same VLAN) or trunk mode (voice and data in separate VLAN) .

Correct ?

LVL 29

Accepted Solution

Predrag Jovic earned 500 total points
ID: 40627424
Almost correct.

Whether the port on Cisco phone will operate as "access" or "trunk" depends on the negotiation with Catalyst switch. You setup port on catalyst switch - phone will adapt.

Author Closing Comment

ID: 40629792

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