Cisco 2950 24 Configuration Guide - Page 331

Chapter 13 Configuring QoS 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 The intelligent wiring closet in Figure 13-4 is composed of Catalyst 2950 switches. 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 gigabitethernet0/1 Step 13 Step 14 Step 15 service-policy input videopolicy exit interface gigabitethernet0/2 Step 16 wrr-queue bandwidth 1 2 3 4 Step 17 wrr-queue cos-map 4 6 7 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 a 8-K burst size. Return to policy-map configuration mode. Return to global configuration mode. Enter interface configuration mode, and specify the ingress interface. Apply the policy to the ingress interface. Return to global configuration mode. Enter interface configuration mode, and specify the egress interface (to configure the queues). 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. 78-11380-03 Catalyst 2950 Desktop Switch Software Configuration Guide 13-27