Vlan based QoS

[sirroutesalot]

Relative to a Cisco 3750 access switch using vlan based QoS on the switchport, can some describe how the switch maps the VLAN to a specific priority level. Example config:

interface GigabitEthernet1/0/1
switchport access vlan 25
switchport mode access
switchport voice vlan 28
mls qos vlan-based
spanning-tree portfast

There must be a mapping required somewhere to associate vlan 28 with priority treatment and vlan 25 with default treatment. I'm just not sure how that mapping is created. Any input?

There are no access lists (other than basic security), policy maps, or class maps on the switch. My assertion to this customer is that he has an incomplete QoS configuration and has failed to properly establish a trust boundary at this port. I'm trying to verify my case before I make this statement to him.

I'm unable to find any Cisco reference to vlan-based QoS other than documents relative to using it for Policing, which is not his goal.

 

[chieftan]

Are you trying to use DSCP or something similar?

 

[chieftan]

This is a very large area to deal with on one page.

Cisco explain this very well at the following location:-

http://www.cisco.com/en/US/customer...figuration_guide_chapter09186a008050245d.html

However, you will need a CCO username and password to access this.

I would copy and paste but it is a large document. If you need me to e-mail it in PDF then let me know.

 

[sirroutesalot]

The goal is to classify on this edge switch based on CoS or DSCP. The connected device can supply both. I typically configure the QoS at the physical port using an "MLS QOS Trust CoS" statement at the port, then use the DSCP-COS map to get the DSCP marked correctly

What I'm having trouble with how the classifying / marking process works when "MLS QOS VLAN-BASED" is configured on the port. How does the switch no that traffic tagged a given vlan gets classfied / marked a certain way?