Configuring QoS with Cisco 3750/4500

Dear expert,

I have a 50 Mbps optical link between 2 remote locations, this optical link is leased to a local telco company. One location is using a Cisco 4503 and port GE 2/15 is connected to the telco switch providing the optical fiber. The other location is using a Cisco 3750 where port 1/0/5 is connected to the telco switch providing the optical fiber.

The network is flat between the remote locations, the same subnet. I am trying to apply some sort of QoS on this link.

I would like to guaranteed 1 Mbps for VOIP, 40 Mpbs for APPLICATION1, 6 Mbps for APLICATION2 and 3 Mbps for default traffic.

I would like this QoS to be shared, not shaped. You will find bellow what I plan to configure on both switches (4503 and 3750),  if someone could review it and give me some advices I would really appreciate. Thanks.

Step1:  Activating QoS

mls qos

Step 2: Match traffic

access-list 20 remark APPLICATION2
access-list 20 permit ip host
access-list 20 permit ip host

access-list 21 remark APPLICATION1
access-list 21 permit ip host
access-list 21 permit ip host
access-list 21 permit ip host

Step3: Classify traffic

class-map match-any APPLICATION1
      match access-group 21
class-map match-any APPLICATION2
      match access-group 20
class-map match-any VOIP
      description VOIP TRAFFIC CLASS
      match ip dscp ef

Step4: Mark traffic

policy map Assign.DSCP
      class VOIP
            set dscp ef
      class APPLICATION2
            set dscp 34
      class APPLICATION1
            set dscp 26
Default traffic will be assigned DSCP 0

Step5: Apply policy to all switch ports

service-policy input Assign.DSCP

Step6:  Mapping DSCP with egress queues

Will use the default mapping. Verify it with show mls qos maps dscp-output-q

DSCP 46 (VOIP) go to queue 1, guaranteed 2% of 50 Mbps.
DSCP 0 (DEFAULT) go to queue 2, guaranteed 6% of 50 Mbps.
DSCP 26 (APPLICATION1) go to queue 3, guaranteed 80% of 50 Mbps.
DSCP 34 (APPLICATION2) go to queue 4, guaranteed 12% of 50 Mbps.

srr-queue bandwidth share 2 6 80 12

Step7: Enabling  priority queue 1 on link egress ports: Port 1/0/5 on 3750 and GE 2/15 on

priority-queue out

Step8: Limits interface speed to the offered link speed by the telco

srr-queue bandwidth limit 5

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luc_roySystem AdminCommented:
OK sorry it took so long I have been looking at this for a few days but i needed to get home and try it on a switch.  The logic and programming are sound.  I am not sure what IOS you are using but here are the changes you would need to make for a newer IOS.

On your “access-list 21 permit host” remove the word IP
On your “policy map Assign_DSCP” you cannot have spaces in the description

Over all it’s a good config that will yield the results you are looking for.

Also this website has a great QOS template in Excel that will help you knock these out in seconds next time.

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mikael42Author Commented:

Thanks a lot for your help, I am going to have a look in a few hours. Thanks again.

luc_roySystem AdminCommented:
no problem, let me know how it works out :)
luc_roySystem AdminCommented:
question was answered, should not be deleted just closed and points awarded.
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