Section 8: QoS (8 Points)

• Configure your switch to trust DSCP QoS from the Cisco IP phones.

You first need to enable QoS for the 3550 with the command mls qos and then under the Cisco IP Phone interfaces (port 0/16 and 0/17), configure mls qos trust dscp. If you have configured this correctly, you have scored 2 points. Example 2-77 shows the Cisco IP phone port QoS summary.

Example 2-77. Switch1 Port 0/16 and 0/17 QoS Summary

 Switch1#sh mls qos int fastEthernet 0/16 FastEthernet0/16 trust state: trust dscp trust mode: trust dscp COS override: dis default COS: 0 DSCP Mutation Map: Default DSCP Mutation Map trust device: none Switch1#sh mls qos int fastEthernet 0/17 FastEthernet0/17 trust state: trust dscp trust mode: trust dscp COS override: dis default COS: 0 DSCP Mutation Map: Default DSCP Mutation Map trust device: none 

• Ensure your switch does not trust QoS from the OEM IP phone.

By default, the switch will not trust the QoS values unless configured to do so as shown in Example 2-77. If you have not configured any option here, you have scored 1 point. Example 2-78 shows the QoS port summary for port 0/18.

Example 2-78. Switch1 Port 0/18 QoS Summary

 Switch1#sh mls qos int fastEthernet 0/18 FastEthernet0/18 trust state: not trusted trust mode: not trusted COS override: dis default COS: 0 DSCP Mutation Map: Default DSCP Mutation Map trust device: none 

• You have a requirement to connect a PC that will be used in your office reception in the future. You have not been told the speed requirements or which VLAN this should be assigned to. You have been told that the PC will connect to port 0/15 on your 3550 and that a policy will be required to ensure that an IP precedence of critical is assigned to web traffic to an intranet server on 172.16.0.9; configure your switch appropriately.

You need to configure a policy that matches on http traffic to destination host 172.16.0.9 on port 0/15; this traffic should then be assigned an IP precedence value of 5. If you have configured this correctly as shown in Example 2-79 you have scored 4 points. Example 2-80 shows the associated QoS policy summary for port 0/15.

Example 2-79. Switch1 Port 0/15 Policy

 class-map match-all intranet   match access-group 100 ! ! policy-map intranet   class intranet     set ip precedence 5 ! interface FastEthernet0/15  no ip address  service-policy input intranet ! access-list 100 permit tcp any host 172.16.0.9 eq www 

Example 2-80. Switch1 Port 0/15 QoS Summary

 Switch1#sh mls qos int fastEthernet 0/15 FastEthernet0/15 Attached policy-map for Ingress: intranet trust state: not trusted trust mode: not trusted COS override: dis default COS: 0 DSCP Mutation Map: Default DSCP Mutation Map trust device: none 

NOTE

As you have not been told which VLAN this port should belong to, it will, by default, belong to VLAN1.

• Configure your voice to be of IP precedence flash value.

Simply configure ip precedence 3 within R1 and R4 VoIP dial-peer statements. If you have configured this correctly, you have scored 1 point.