Cisco 2950 Software Configuration Guide - Page 601

Chapter 30 Configuring QoS Standard QoS Configuration Examples For the Catalyst 2900 and 3500 XL switches, CoS configures each transmit port (the egress port) with a normal-priority transmit queue and a high-priority transmit queue, depending on the frame tag or the port information. Frames in the normal-priority queue are forwarded only after frames in the high-priority queue are forwarded. Frames that have 802.1p CoS values of 0 to 3 are placed in the normal-priority transmit queue while frames with CoS values of 4 to 7 are placed in the expedite (high-priority) queue. QoS Configuration for the Intelligent Wiring Closet Figure 30-5 shows an intelligent wiring closet with Catalyst 2950 switches, for example. One of the switches is connected to a video server, which has an IP address of 172.20.10.16. The object of this example is to prioritize the video traffic over all other traffic. To do so, a DSCP of 46 is assigned to the video traffic. This traffic is stored in queue 4, which is serviced more frequently than the other queues. Beginning in privileged EXEC mode, follow these steps to configure the switch to prioritize video packets over all other traffic: Step 1 Step 2 Command configure terminal access-list 1 permit 172.20.10.16 Step 3 class-map videoclass Step 4 match access-group 1 Step 5 exit Step 6 policy-map videopolicy Step 7 class videoclass Step 8 set ip dscp 46 Step 9 police 5000000 8192 exceed-action drop Step 10 Step 11 Step 12 exit exit interface interface-id Step 13 Step 14 Step 15 Step 16 service-policy input videopolicy exit wrr-queue bandwidth 1 2 3 4 wrr-queue cos-map 4 6 7 Step 17 end Purpose Enter global configuration mode. Define an IP standard ACL, and permit traffic from the video server at 172.20.10.16. Create a class map called videoclass, and enter class-map configuration mode. Define the match criterion by matching the traffic specified by ACL 1. Return to global configuration mode. Create a policy map called videopolicy, and enter policy-map configuration mode. Specify the class on which to act, and enter policy-map class configuration mode. For traffic matching ACL 1, set the DSCP of incoming packets to 46. Define a policer for the classified video traffic to drop traffic that exceeds 5-Mbps average traffic rate with an 8192-byte burst size. Return to policy-map configuration mode. Return to global configuration mode. Specify the switch ingress interface that is connected to the video server, and enter interface configuration mode. Apply the policy to the ingress interface. Return to global configuration mode. Assign a higher WRR weight to queue 4. Configure the CoS-to-egress-queue map so that CoS values 6 and 7 select queue 4. Return to privileged EXEC mode. 78-11380-10 Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide 30-41