Cisco 300 QoS for VoIP

[tthomast04]

I have a question about best practice to priotize voice packets on the LAN side.

We have everything configured on the firewall/edge device for voice prioritization, however I am unsure of the exact steps to take on the LAN side to make sure that traffic within the LAN will not affect voice quality.

Our setups a very basic: vlan 1 (default) for data, and vlan 100 (voice) - The ports are configured as General (1untagged, 10tagged).

At this point the phones are manually set with a vlan, but form reading these forums I see I can accomplish this by setting up LLDP and having it automatically assigned the vlan instead of manually setting this,

My main concern, however as stated above, is QoS.

Does anyone have a best practice or some advice on how to setup QoS specifically for voice.

I found this pdf, however I was unsure where they came up with the CIR and CBS values.

https://supportforums.cisco.com/docs/DOC-13461

This is my first post to the forums; thanks in advance for any help provided.

[Tom Watts]

hi tthomas, by default the switch employs basic QoS based off VLAN tag. So long as your phone is using a tag packet, QoS is automatically applied.

If you'd like more control, here is a different document to use LLDP-MED and how to configure it

https://supportforums.cisco.com/docs/DOC-27005

-Tom
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[tthomast04]

I have manually tagged the phones on 10, however how does the switch know to get priority to vlan 10 if congestions, etc occurs?

Thanks,

[Tom Watts]

802.1p

-Tom
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[tthomast04]

The computer are on the native vlan 1 and the phones are on vlan 10. Smartport is disabled. Isn't there a setting to tell it that vlan10 get's priority over everything else, etc?

[Tom Watts · Accepted solution]

Hi Thomas, this is done automatically through the basic QoS. Within a VLAN tag packet, these is a PCP value (3 bit). When the switch receives such frame it will honor the value based off that PCP value.

-Tom
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http://blogs.cisco.com/smallbusiness/