Daren Matthews

Here are some QoS examples configured on a Cisco Catalyst 3550:

1. mls qos
### enables qos globally#######

2. mls qos cos-map 0 8 16 26 34 46 48 56
### maps cos values to dscp values properly######

3. For IP phones ports, apply the following commands

int range fa 0/1 , fa 0/2
#### ip phone ports

flowcontrol receive off ***** important command********
flowcontrol send off *********important command*******

4. Mapping voice bearer traffic in priority queue

int fa0/1

wrr-queue cos-map 4 5
priority-queue out
### if asked to put Voice bearer in priority queue

5. Mapping voice signalling traffic in queue 3

wrr-queue cos-map 3 3

6. Port configuration

interface fa0/1

mls qos trust cos
#### trusts packet cos
mls qos trust device cisco-phone
#### trusts cos only if a phone is attached

switchport priority extend cos 0

### zeros out PC cos values.

7. If asked to modify bandwidth and buffer settings for each queue (only then do the following)

For fastE ports:

mls qos min-reserve 5 170
mls qos min-reserve 6 130
mls qos min-reserve 7 51
mls qos min-reserve 8 34
#### defines min-reserve levels (upto 8 levels may be defined, default buffer size is 100 for all levels)####

int range fa 0 /1, fa 0/2

wrr-queue bandwidth 20 20 60 1
### priority queue doesnt need wrr bandwidth allocation
wrr-queue min-reserve 1 5
wrr-queue min-reserve 2 6
wrr-queue min-reserve 3 7
wrr-queue min-reserve 4 8
### maps min-reserve levels to queues#####

For GigE ports:

int range gi 0/1 , gi 0/2
wrr-queue queue-limit 60 20 20 1
#### defines more buffer space for low priority queue ####
wrr-queue bandwidth 20 20 60 1

8. DSCP maps (optional)

For gig ports there is a dscp map that maps dscp values to thresholds.
Each queue has two thresholds, and by default all dscp values are mapped to threshold 1.
If asked to set voice traffic (may be video) to threshold 2, use command.

wrr-queue dscp-map 2 26 34 46 (this is higher threshold in the queue)

9. Tail Drop or WRED (optional)

For gig ports default drop mechanism is tail drop. Here is how you may modify these thresholds:

wrr-queue threshold 1 80 100
wrr-queue threshold 2 80 100
wrr-queue threshold 3 80 100

### no need to define drop thresholds for queue 4 if its priority queue

To enable WRED and specify thresholds, use following commands:

wrr-queue random-detect max-threshold 1 80 100
wrr-queue random-detect max-threshold 2 80 100
wrr-queue random-detect max-threshold 3 80 100

### WRED and tail drop are mutually exclusive

10. Classification using ACLs.

To classify based on subnet, define standard or extended acl’s.

access-list 101 permit ip any any dscp 24

class-map test
match access-group 101

11 .Defining Policer and Remarking traffic
mls qos map policed-dscp-map 26 46 to 0
#### remarks voice control and bearer traffic to dscp 0. (Defined in policer)

mls qos aggregate-policer TestPolicer 256000 8000 exceed-action policed-dscp-transmit
#### defines an aggregate policer with a rate of 256kbps, burst of 8000 bits and remarks dscp for voice and bearer traffic based on above policed-dscp map
class-map match-all Voice
match ip dscp af31 ef

policy-map Voice
class Voice
trust dscp
police aggregate TestPolicer
#### applies aggregate policer to the class.
You cannot define same policer across multiple policy-maps.

int range fa 0/1 , fa0/2
service policy input Voice

Example configs:

1. To define a class-map that remarks traffic:
——————————————
class-map match-all VoiceControl
match ip dscp af31
class-map match-all VoiceBearer
match ip dscp ef

policy-map Voice
class VoiceControl
trust dscp
set ip dscp 40
class VoiceBearer
trust dscp
set ip dscp 24
int range fa 0/1 , fa0/2
service policy input Voice

2 . To perform per-vlan, per-port classification, marking, policing. (may be required on gateway ports which may be a trunk port)
—————————————————————
class-map match-all Voice
match ip dscp af31 ef

class-map match-all VoiceVLAN
match vlan 100 ————– defines which vlan you want to match
match class-map Voice ——- defines all traffic on voice vlan with dscp af31 or ef.
policy-map Voice
class VoiceVLAN
trust dscp
police aggregate TestPolicer

#### applies aggregate policer to vlan 100
You cannot define same policer across multiple policy-maps.

int range fa 0/3
Decription Gateway port
service policy input Voice

3. To perform individual policing on each class:
———————————————-

mls qos map policed-dscp-map 26 46 to 0

class-map match-all Voice
match ip dscp af31 ef

policy-map Voice
class Voice
trust dscp
police 256000 8000 exceed-action policed-dscp-transmit
####This is a individual policer

int range fa 0/1 , fa0/2
service policy input Voice

Source:
CCIE Voice Notes at:
http://cciev.wordpress.com/2006/05/25/qos-templates-for-3550/