how to trust both phone and softphone qos cos marking?

[ggovier]

Okay, I have an installation where the switch access port faces a phone (7942 or 7962) with a subtended PC.

The PC is also running a Cisco softphone (IP Communicator).

The switch config has the option of programming the port to trust either a phone OR a softphone

Switch(config-if)#auto qos voip ?

  cisco-phone      Trust the QoS marking of Cisco IP Phone

  cisco-softphone  Trust the QoS marking of Cisco IP SoftPhone

  trust            Trust the DSCP/CoS marking

I know that the switch uses CDP to recognise either in order to trust it.

I like the idea of CDP checking for a trusted source of QOS markings.

How can I make the port work with both a cisco-phone AND a cisco-softphone, without just trusting all DSCP marking (like from other apps on the PC)?

Or asking another way,

• does the "cisco-softphone" setting exclude trusting a cisco phone?
• does the "cisco-phone" setting exclude trusting a cisco softphone?

I have not sniffed it, but there is a voiuce VLAN for the phone, and a data VLAN for the PC. I'm assuming the softphone uses the data vlan.

Thanks

[paolo bevilacqua]

To make it realy easy, leave the defaul of "no mls qos". The switch will not mess with DSCP values, and everything will work great.

Try to believe

[James Hawkins]

Hi,

The definitions below are taken from the Cisco Enterprise QoS SRND:

The standard (interface) configuration commands to enable AutoQoS are: auto qos voip. Depending on the platform, AutoQoS VoIP can support the following additional keyword commands:

• cisco-phone—When you enter the auto qos voip cisco-phone interface  configuration command on a port at the edge of a network that is  connected to a Cisco IP Phone, the switch enables the  conditional-trusted boundary feature. The switch uses the Cisco  Discovery Protocol (CDP) to detect the presence or absence of a Cisco IP  Phone. When a Cisco IP Phone is detected, the ingress classification on  the interface is set to trust the CoS marking of the received packet.  When a Cisco IP Phone is absent, the ingress classification is set to  not trust the CoS (or DSCP) value of any packet.

• cisco-softphone—When you enter the auto qos voip cisco-softphone interface  configuration command on a port at the edge of the network that is  connected to a device running the Cisco SoftPhone, the switch uses  policing to decide whether a packet is in or out of profile and to  specify the action on the packet. If the packet does not have a DSCP  value of 24, 26, or 46 or is out of profile, the switch changes the DSCP  value to 0.

So it looks like the cisco-phone variant works with CDP and the cisco-softphone variant just polices the call payload and signalling traffic to what is acceptable for a single call - it does not do any detection of whether the attached PC is running the IP communicator software. You should therefore just be able to use the cisco-softphone for all ports regardless of whether they are supporting a physical phone or softphone.

I would however be tempted not to trust the attached device at all and writea bespoke config rather than relying on auto-qos. The link below should get you started doing this.

http://www.cisco.com/en/US/docs/solutions/Enterprise/WAN_and_MAN/QoS_SRND/QoSDesign.html#wp1055786