BCMSN Lab 7-1 Configuring Switches for IP Telephony Support

I actually found this to be more HSRP labbing than anything else!  The main point of this lab however was to set up a L3 switched network with AutoQOS enabled on a couple choice interfaces.  Basically you have 2 L3 switches running HSRP on 3 vlans:

• VLAN 100- Data Vlan
• VLAN 200- Voice Vlan
• VLAN 1 - Management Vlan

The HSRP config was simple.  I should be able to do this in my sleep now, including most of the advanced features of it and it's associated debugging commands.  These two L3 switches (my distribution layer) had 1 access layer switch connected to them (both with etherchannels configured).  There were suppose to be 2 access switches, but I ran out of crossover cables!  Anywho,  they had me set a VOIP phone off of port fa0/6 on the access switch.  My config was as follows:

int fa0/6

switchport access vlan 100

switchport voice vlan 200

auto qos voip cisco-phone

end

Everything there should be relatively self-explanatory except the fourth line.  Let me tell you whats going on with that auto qos voip cisco-phone command.  First know that the auto qos command is actually a macro that runs when you hit enter.  Multiple line are sent to the switchport.  Check it out:

2950#sh run int fa0/6
interface FastEthernet0/6
 switchport access vlan 100 - data vlan
 switchport voice vlan 200 -  voice vlan
 mls qos trust device cisco-phone - This sets the cos trust on a dependency that a cisco voip phone will be on the other end. 
 mls qos trust cos - this just says "trust the cos value sent to you from the device"..i.e. the cisco phone which sets a cos value of 5 by default
 auto qos voip cisco-phone - I entered this to generate everything else.
 spanning-tree portfast - cumon!  Good to know it executes this as well though!
end

    OK, so your probably like what the hell do those mean!  To be honest, I was too.  I went out and read about them, and will attempt to give an explanation here (both for your benefit and mine!).  I put the notes above next to the command outputs. 

 Not to mention the commands set in the global config
wrr-queue bandwidth 10 20 70 1 (sets the bandwidth values for queue 1,2,3,4 (10, 20, 70, 1) "The ratio of the weights is the ratio of frequency in which the WRR scheduler dequeues packets from each queue."
wrr-queue cos-map 1 0 1 (cos values of 0 and 1 are mapped to queue 1)
wrr-queue cos-map 2 2 4 (cos values of 2 and 4 are mapped to queue 2)
wrr-queue cos-map 3 3 6 7 (cos values of 3, 6 and 7 are mapped to queue 3)
wrr-queue cos-map 4 5 (cos values of 5 are mapped to queue 4)
mls qos map cos-dscp 0 8 16 26 32 46 48 56 (maps cos values to differentiated service code point values...this is the default mapping enabled by auto qos)

and a little show command:

2950#sh mls qos int fa0/6
FastEthernet0/6
trust state: not trusted - a phone is NOT connected
trust mode: trust cos
COS override: dis
default COS: 0 - default is 0, however the COS of 5 will be accepted from a voip phone
pass-through: none
trust device: cisco-phone


Most of the detailed QOS stuff is outside the scope of the BCMSN exams, but I thought I should touch on it now so that it isnt a total shock when I hit the topics down the road.  Verify your voice vlans and appliance trusts here:
2950#sh int fa0/6 switch
Name: Fa0/6
Switchport: Enabled
Administrative Mode: dynamic desirable
Operational Mode: down
Administrative Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 100 (100)
Trunking Native Mode VLAN: 1 (default)
Voice VLAN: 200 (200)
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk private VLANs: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none - I have not extended the trust boundary beyond the cisco phone using the switchport priority extend trust command.  Look after I execute it:
2950#sh int fa0/6 switch
Name: Fa0/6
Switchport: Enabled
Administrative Mode: dynamic desirable
Operational Mode: down
Administrative Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 100 (100)
Trunking Native Mode VLAN: 1 (default)
Voice VLAN: 200 (200)
\output omitted\
Appliance trust: trusted

The last thing I did was enable the distribution switches to trust my cos information being sent in the L2 frames using the commands:

(config)mls qos - enable it globally

(config-if)auto qos voip trust - trust the incoming qos values