CCNP Switch Lab 7-1 Configuring Switches for IP Telephony Support

CCNP Switch Lab 7-1 Configuring Switches for IP Telephony Support




  • Configure auto QoS to support IP phones.
  • Configure CoS override for data frames.
  • Configure the distribution layer to trust access layer QoS measures.
  • Manually configure CoS for devices that cannot specify CoS (camera).
  • Configure HSRP for voice and data VLANs to ensure redundancy.
  • Configure 802.1Q trunks and EtherChannels for Layer 2 redundancy and load balancing.

IP phones have been deployed throughout the network. Each phone is connected to an access port on a 2960 Cisco switch. Each user PC is connected to the network using the IP phone internal switch so that the phones can be deployed without additional wiring.

Note: The access layer switches depicted in the topology are assumed to support PoE for the IP phones. However, the switches used in this lab do not support PoE. This will not affect the commands used in this lab.

In this lab, you configure the quality of service (QoS) on the access and distribution layer switches so that they trust the class of service (CoS) mapping provided by the IP phone through Cisco Discovery Protocol (CDP). To ensure redundancy for the phones and user end stations, you will use Hot Standby Router Protocol (HSRP) on the distribution layer switches.

A camera for video is also deployed on the network, which requires that its access port on the 2960 be manually configured. It is not necessary to have an IP phone or camera to successfully complete the lab. The focus is on the configuration of access and distribution layer switches to support QoS for these devices.

Note: This lab uses Cisco WS-C2960-24TT-L switches with the Cisco IOS image c2960-lanbasek9-mz.122- 46.SE.bin, and Catalyst 3560-24PS with the Cisco IOS image c3560-advipservicesk9-mz.122-46.SE.bin. You can use other switches (such as a 2950 or 3550) and Cisco IOS Software versions if they have comparable capabilities and features. Depending on the switch model and Cisco IOS Software version, the commands available and output produced might vary from what is shown in this lab.

Required Resources

  • 2 switches (Cisco 2960 with the Cisco IOS Release 12.2(46)SE C2960-LANBASEK9-M image or comparable)
  • 2 switches (Cisco 3560 with the Cisco IOS Release 12.2(46)SE C3560-ADVIPSERVICESK9-mz image or comparable)
  • Host PC (optional)
  • IP phone (optional)
  • Camera (optional)
  • Ethernet and console cables

Step 1: Prepare the switches for the lab.
Erase the startup configuration, delete the vlan.dat file, and reload the switches. Refer to Lab 1 -1, “Clearing a Switch” and Lab 1 -2, “Clearing a Switch Connected to a Larger Network” to prepare the switches for this lab.Cable the equipment as shown.

Step 2: Configure basic switch parameters.
Configure the management IP addresses in VLAN 1, and the hostname, password, and Telnet access on all four switches. Also configure a default gateway on the access layer switches. The distribution layer switches act as Layer 3 devices and do not need default gateways.

Step 3: Configure the trunks and EtherChannels.
Configure the trunks according to the diagram, and configure EtherChannels between the switches. Using EtherChannel for the trunks provides Layer 2 load balancing over redundant trunks.

a. The following is a sample configuration for the trunks and EtherChannel from DLS1 to the other three switches. Notice that the 3560 switch needs the switchport trunk encapsulation {dot1q | isl} command, because this switch also supports ISL encapsulation.

b. The following is a sample configuration for the trunks and EtherChannels from DLS2 to the other three switches.

c. The following is a sample configuration for the trunks and EtherChannel from ALS1 and ALS2 to the other switches.

d. Use the show interfaces trunk command on all switches to verify the trunks. Which VLANs are currently allowed on the newly created trunks?
All VLANs existing in the switch VLAN database.

e. Use the show etherchannel summary command on each switch to verify the EtherChannels. Which EtherChannel negotiation protocol is in use here?
LACP is the EtherChannel negotiation protocol in use. This is the result of the channel-group x mode being set to active.

Step 4: Configure VTP on ALS1 and ALS2.
a. Change the VTP mode of ALS1 and ALS2 to client.

b. Verify the VTP changes with the show vtp status command.
How many VLANs can be supported locally on the 2960 switch?
Up to 255 VLANs can be supported locally on the 2960 switch.

Step 5: Configure VTP and the VLANs on DLS1.
a. Create the VTP domain on DLS1, and create VLANs 10, 20, and 30 for the computer data, voice, and video VLANs in the domain.

b. Verify the VTP information throughout the domain using the show vlan and show vtp status commands.
How many existing VLANs are in the VTP domain?
There should be eight VLANs: five existing built-in VLANs and three new ones that were just created.

Step 6: Configure IP routing, VLAN SVIs, and HSRP on DLS1 and DLS2.
a. Configure HSRP between the VLANs to provide redundancy in the network. To achieve some load balancing, use the standby [group] priority command. Use the ip routing command on DLS1 and DLS2 to activate routing capabilities on the switch.

Each route processor will have its own IP address on each switched virtual interface (SVI) and also be assigned an HSRP virtual IP address for each VLAN. Devices connected to VLANs 10, 20, and 30 use the gateway IP address for the VLANs.

The standby command is also used to configure the IP address of the virtual gateway and configure the router for preemption. The preempt option allows for the active router with the higher priority to take over again after a network failure has been resolved.

Notice in the following configurations that the priority for VLANs 1 and 10 has been configured for 150 on DLS1, making DLS1 the active router for those VLANs. VLANs 20 and 30 have been configured for a priority of 100 on DLS1, making DLS1 the standby router for these VLANs. Reverse priorities have been configured on the VLANs on DLS2. DLS2 is the active router for VLANs 20 and 30, and the standby router for VLANs 1 and 10.
HSRP Configuration for DLS1

HSRP Configuration for DLS2

b. Enter the show standby brief command on both DLS1 and DLS2.
Which router is the active router for VLANs 1 and 10? Which is the active router for VLAN 20?
The active router on VLANs 1 and 10 is DLS1. The active router on VLAN 20 is DLS2.

How is the active HSRP router selected?
If preemption is enabled, the highest priority router becomes the active router. If preemption is not enabled, the highest priority router might have to wait for the current active router to go down if the highest priority router is not in that position already.

c. Enter the show standby command on both DLS1 and DLS2.
What is the default hello time for each VLAN? What is the default hold time?
The default HSRP hello time is 3 seconds. The default HSRP hold time is 10 seconds.

d. Verify routing using the show ip route command. The following is sample output from DLS1.

Step 7: Configure access ports to trust IP phone CoS.
The access layer switches will be the QoS trust boundaries for the network. Data coming in on the switch ports will either have the CoS trusted or altered based on the information received on the ports.

Configure Fast Ethernet access ports 15 to 24 to trust the CoS for recognized IP phones on the network. The CoS of a Cisco IP phone is 5 by default. Any port that has a device other than a Cisco phone will not trust the CoS that is advertised. This configuration is accomplished by using the Cisco auto QoS features offered on these switches. Using a single command at the interface level, you can implement both trust boundaries and QoS features. Information obtained through CDP is used to determine when an IP phone is attached to the access port.

The following configuration also sets the voice VLAN on the interface with the switchport voice vlan vlannumber command.
Configure Fast Ethernet ports 15 through 24 on ALS1 and ALS2 using the interface range command.

Note: Configuring auto QoS on an interface automatically adds global mls qos srr-queue, class-map and policy-map commands to the running configuration. A number of interface-specific command are also added,
including spanning-tree portfast.

Step 8: Verify the access layer auto QoS configuration.
Verify the auto QoS configuration at the access layer using the show mls qos interface interface-type interface-number and show run commands.

What is the default CoS for a PC connected to these interfaces?
The default CoS for a PC connected to these interfaces is 0, because it will be an untrusted device.

Step 9: Configure the distribution layer switches to trust access layer CoS.
Configure the distribution layer switches to trust the CoS information in the Layer 2 frames being sent from the access layer. Because the trust boundary is at the access layer, frames being sent from this layer should be trusted into the distribution layer for optimal QoS.

Step 10: Verify the distribution layer auto QoS configuration.
a. Verify auto QoS at the distribution layer on DLS1 and DLS2 using the show auto qos interface command.

b. Use the show mls qos interface fastEthernet interface ID command on DLS1 to verify QoS on the trunk interfaces.

Step 11: Manually assign access layer CoS for the camera.
A camera needs to be moved from its current location in the network and connected to FastEthernet0/5 of ALS2.

Video traffic must have priority treatment within the network, because it has different requirements than data or voice traffic. The priority of the video traffic will be configured to be lower than the priority of the voice traffic.

a. Because the camera is not capable of setting its own CoS, assign a CoS of 3 to ensure that the video traffic is identified by other switches and routers within the network.

b. Verify the configuration using the show mls qos interface command on ALS2.

Device Configurations (Instructor version)
Switch DLS1

Switch DLS2

Switch ALS1

Switch ALS2

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