Class based Qos


I am doing a test for prioritizing SSH and Port 60 traffic using bandwidth shape up to 1.5 Mbps over 2 Mbps backhaul link, other traffic should pass through remaining BW = 512 kbps, and I would apply this QoS (service policy) in backhaul router WAN interface. how do I achieve this with Cisco QoS.

(Lazaros Agapides) #2

Hello Sivakumar

I suggest you go through Rene’s section on QoS and traffic shaping and see if you can apply some of the concepts there to your topology. Take a look at:

as well as at the various other QoS lessons.

Once you make your attempt, if you hit a snag or have any more specific questions, we’re here to help!

I hope this has been helpful!



Thanks for the reply. Yes I gone through Rene’s Qos shaping, but that steps will not work in 15(4) IOS, I can’t associate service policy directly to the interface instead need to create parent child policy and associated to the interface. Please help to create Parent child policy where I can prioritize and BW shaped

(Rene Molenaar) #4

Hi Sivakumar,

You can’t configure a priority queue and shape in a single policy-map. You’ll need a nested policy for that. Here’s an example:

ip access-list extended TCP_60
 permit tcp any any eq 60

class-map match-any PRIORITY
 match access-group name TCP_60
 match protocol ssh

policy-map PRIORITY
 class class-default
  priority 1000
policy-map SHAPER
  shape average 1500000
   service-policy PRIORITY

The parent policy is a shaper for SSH / TCP 60 traffic and it shapes up to 1.5 Mbps. The sub-policy (PRIORITY) has a priority queue. I’ve set it to 1 Mbit.

All SSH / TCP 60 traffic is shaped up to 1.5 Mbit and prioritized up to 1 Mbit. Why do you want to shape up to 1.5 Mbit btw? Do you want to prevent drops from when you exceed 2 Mbit?

In that case, it would make more sense to configure it like this:

policy-map SHAPE_ALL
 class class-default
  shape average 2000000   
   service-policy PRIORITY

policy-map PRIORITY
  priority 1500

Now you shape everything up to 2 Mbit. Within the shaper, the sub-policy adds a priority queue for your SSH and TCP_60 traffic.