Help with prioritizing voice vlan on catalyst

[hoosier2933]

Hello, I could use some help on prioritizing voice across my switches. I have done a lot of research but im not sure some of what I saw is all necessary. In my setup i have a few catalyst 2960's and using a 3650 core. I have vlan 10 (data) and vlan 20 (voice) setup already and my interfaces setup as switchport access vlan 10 and also switchport voice vlan 20. My question, what else do I need to do to make sure that vlan 20 gets priority on the switch? I dont need to prioritize any other traffic from any other vlan, just voice. I use IP phones but they arent cisco, so I dont think anything would really happen automatically as far as qos or anything. Im fine on getting the phones onto the voice vlan, just looking to make sure anything on vlan20 gets priority across the switches in my local environment. I appreciate any help, thanks very much in advance.

[balaji.bandi]

here is the campus design guide with sample config for QOS

https://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/WAN_and_MAN/QoS_SRND/QoS-SRND-Book/QoSDesign.html

[hoosier2933]

Thank you for your replies, i wanted to read through all of this before responding. It seems you can get real deep into qos, but in my case it seems that I only need to use the auto qos voip trust command on the interfaces. That would automatticaly generate the config below in the interfaces, does that sound right? I will have a non cisco voip phone with a pc attached to that phone on the switch interfaces. The phone itself is capable of tagging the voice vlan20, so it will be on the voice vlan and grab an address from the voice vlan dhcp. Since its capable of doing that, i dont need to worry about cdp or lldp In that case right? Would i be all set for making sure that the voice traffic coming from the IP phone will get priority over the data coming from the pc's on data vlan 10? Thanks again for the assistance.

The switch automatically enables standard QoS and configures the CoS-to-DSCP map (maps CoS values in incoming packets to a DSCP value).

CAT2950(config)# mls qos map cos-dscp 0 8 16 26 32 46 48 56

If you entered the auto qos voip trust command, the switch automatically sets the ingress classification on the interface to trust the CoS value received in the packet.

CAT2950(config-if)# mls qos trust cos

[Giuseppe Larosa]

Hello hoosier2933,

>> Since its capable of doing that, i dont need to worry about cdp or lldp In that case right? 

I don't think this is right the switch with autoqos would like to discover attached IP phones either using CDP or LLDP MED.

It is not only a question of getting an IP address from the voice vlan pool.

For all other QoS tasks that your switch should perform you should refer to Joseph's post that has explained already what is needed.

There is another thread where a user has deployed third party IP phones and and then AutoQoS and the autoQoS outbound policy is not matching a packet in the priority queue (LLQ)!

So it is not so plug and play as you might think.

Hope to help

Giuseppe

[hoosier2933]

Thanks for the reply. Ok, well my IP phones are capable of using lldp method, just not cdp. Is there a better way to enable lldp on the swtich and still use auto qos for the voice vlan 20 without having to manually do any in depth qos setup on the interfaces? 

[Giuseppe Larosa]

Hello hoosier2933,

conf t

lldp run

Hope to help

Giuseppe

[Joseph W. Doherty]

What else should you do? You should insure your VoIP packets have a ToS marking that allows them to be given service treatment that's needed. You also then need to insure all ports have an egress policy that actually provides service treatment.

For example, normally you insure all VoIP "bearer" packets have a DSCP EF marking. You also insure egress ports place DSCP packets into either PQ or LLQ. Further you insure VoIP "signally" packets are marked (CS3, Cisco recommendation, or CS5, RFC) and "protected" to minimize packet loss and/or extensive delay. (I.e. on a switch you would want [ideally] 3 egress queues. PQ for VoIP bearer. A queue with sufficient bandwidth guarantee for VoIP signally. A queue for everything else.)

Device specific details can be found:
https://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/WAN_and_MAN/QoS_SRND_40/QoSCampus_40.html#pgfId-1098448
https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3650/software/release/16-5/configuration_guide/qos/b_165_qos_3650_cg/b_165_qos_3650_chapter_00.html