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QOS with a 2960S and a Bridge

RadiclDreamer

RadiclDreamer

Diamond Member
I have a pair of cisco 1310 bridges that have a wireless link to a small office less than a mile away from our main site with direct line of sight. I have configured them as root and non root bridge and brought the link up with decent speeds (for wireless) but I anticipate some voice traffic going across the lines and want to implement some QOS for this voice traffic only.

My question is what is the simplest way to do this? I know the ports on the 2960 will need configured as mls qos trust dscp ports but is there anything further that needs done? How about the wireless bridges?
 
You setup QoS on the F0 and radio interfaces. It's straight forward and works like a champ. Should be a doc on Cisco on how to. And then do auto qos trust on the switchports.
 
Wouldnt happen to have a sample handy would you? I've been digging around their site and found TONS of useful information but im getting info overload and am not really sure if some of the things even pertain to me or not.
 
I THINK I have it setup correctly, I told it to assign priority 6 to EF (DSCP 46) and then applied that rule to both the ingress and egress of both the ethernet and the radio interfaces. I now need to run wireshark on it and make sure the tag is getting applied correctly unless you know of an easier way to verify setup?
 
For those interested the config i ended up with was:

#Created a class map called VTraffic and told it to match a DSCP value of 46 or Express Forwarding#


class-map match-all _class_VTraffic0
match ip dscp ef
!
!
#In the policy map i said anything that ended up getting match in the class map to set a COS (class of service) of 6 which is just below the max of 7 that is for network traffic#

policy-map VTraffic
class _class_VTraffic0
set cos 6


#Applied said policy in and out on the Dot11Radio interface, do the same for the ethernet#



interface Dot11Radio0
no ip address
service-policy input VTraffic
service-policy output VTraffic
 
Keep in mind CoS=6 maps to DSCP of 48 by default:

SW1>show mls qos map cos-dscp
Cos-dscp map:
cos: 0 1 2 3 4 5 6 7
--------------------------------
dscp: 0 8 16 24 32 40 48 56

DSCP=46 is typically associated with CoS=5, but you can see from the output above that the switch will translate CoS=5 to DSCP=40 and vice versa unless you A) configure DSCP trust or B) modify the mutation map:

SW1(config)#mls qos map cos-dscp 0 8 16 24 32 46 48 56
SW1(config)#end
SW1#sh mls qos map cos-dscp

Cos-dscp map:
cos: 0 1 2 3 4 5 6 7
--------------------------------
dscp: 0 8 16 24 32 46 48 56

I'm pointing all of this out because you want to ensure that your markings are preserved end-to-end, or you will inevitably end up with a surprise (possibly resulting in dropped calls, etc).
 
RadiclDreamer said:
Nice to know, thanks. I did turn on dscp trust on the switch side, should that have the same effect?
Click to expand...

It will have a similar effect. The switch will use the mapping table I posted in order to calculate DSCP when only a CoS value is present instead of DSCP (ie when CoS is trusted instead of DSCP, or when a policer sets CoS values and not DSCP).

In your case since you are trusting DSCP it will maintain that value on every switch that has trusting configured. It will still use that mapping table to calculate CoS values if you have any .1q links, but that will be A-OK because DSCP=46 maps to CoS=5 by default (just not the other way around).

Isn't QoS fun???
 
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