In part 1 of this series, we examined the class maps that you use to classify traffic you want to make QoS treatments for. In part 2, we took a look at policy maps. These are the structures you use in order to actually make the QoS manipulations with.

But the question remains, how do you assign this QoS policy to an interface in a particular direction. The answer, of course, is service policies. In this post, we examine the service policy step, and ensure we can easily verify a QoS configuration that utilizes the MQC.

Let us walk through a simple example. We will classify a very specific PING using a class map, and then punish it with the drop treatment at a router interface. Let drop ICMP Echo packets sourced from the loopback of R1 at the R2 interface s0/0.

First – let’s make sure out little topology has full connectivity – a PING to the Loopback0 of R1 will do the trick:

R2#ping 1.1.1.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 16/26/40 ms

R2#

Next, let’s create a class map that gathers the Echoes from the Loopback0, and then we will add that to a policy map that drops them. Finally, the new step for our posts here, we will assign this to the int s0/0 of R2 in the inbound direction:

R2(config)#access-list 100 permit icmp host 1.1.1.1 any echo   

R2(config)#class-map match-any CM_ICMP

R2(config-cmap)#match access-group 100

R2(config-cmap)#exit

R2(config)#policy-map PM_ICMP

R2(config-pmap)#class CM_ICMP

R2(config-pmap-c)#drop

R2(config-pmap-c)#exit

R2(config-pmap)#exit

R2(config)#int s0/0

R2(config-if)#service-policy input PM_ICMP

Now, it is time for our verifications! Fun!

R1#ping 2.2.2.2

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 4/15/28 ms

R1#ping 2.2.2.2 source lo0

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds:

Packet sent with a source address of 1.1.1.1 

.....

Success rate is 0 percent (0/5)

R1#

But if you know me, I am pretty paranoid. Was it really out MQC configuration that produced this verification result. Now it is time for the power for the show policy-map interface command. One of my all time favorites:

R2#show policy-map interface s0/0

 Serial0/0 

  Service-policy input: PM_ICMP

    Class-map: CM_ICMP (match-any)

      5 packets, 520 bytes

      5 minute offered rate 0 bps, drop rate 0 bps

      Match: access-group 100

        5 packets, 520 bytes

        5 minute rate 0 bps

      drop

    Class-map: class-default (match-any)

      58 packets, 3912 bytes

      5 minute offered rate 0 bps, drop rate 0 bps

      Match: any 

R2#

Notice this output proves so much. Our class-map did grab those packets, they were properly treated rudely in the policy map, and we of course verified that we assigned all of this correctly.

Thanks for reading this three part series on a review of the MQC. I am heading back in line for Star Wars tickets.