QoS on Cisco 2960 and 3850

[daniel.tanch]

Hi,

I will like to check how to go about to configure QoS for cisco 2960 and 3850. Basically I will need to know what is needed to be configure on the access port and trunk port for both switches. Currently I am using auto QoS, is this the correct way? 

PC(jabber)---Cisco IP Phone---2960---3850---rtr

The access port will be connected to a Cisco IP Phone and from there connected to a PC. User will be using either the PC(jabber) or IP phone for communication. So how does the switch port mark these traffic via jabber and IP phone? Is it possible to trust both the softphone and hardphone? 

The trunk is a uplink to core switch(3850). 

2960

mls qos

!

interface GigabitEthernet0/1

 description Connect to IP Phone

 switchport access vlan 50
 switchport mode access
 switchport voice vlan 56
 duplex full
 priority-queue out
 mls qos trust cos
 spanning-tree portfast

!

interface GigabitEthernet0/48
 description Connected to 3850
 switchport mode trunk
 priority-queue out  
 mls qos trust cos

3850

interface GigabitEthernet1/0/1
description Connected to 2960
switchport mode trunk
auto qos trust
service-policy input AutoQos-4.0-Trust-Cos-Input-Policy
service-policy output AutoQos-4.0-Output-Policy

[Mark Malone]

I would use mls qos trust dscp on the access ports and the uplinks if your 2960 supports as that will trust the DSCP markings fcover video and voice soft or hard and anything else marked at the source in DSCP , ios-xe switches carry DSCP markings by default but what you have enabled will work too on the 3850 its just going to introduce class maps and policies while without it it would just honor the markings coming from the 2960 , so both will work , you can still use cos if you want just make sure the mappings are correct in global config that were auto generated but using DSCP it shouldnt have to be mapped

priority queue out will make sure everything in that queue is serviced first , that can cause starvation sometimes for other traffic as its left as the p queue is emptied so you should be careful with that command depending on your traffic

[daniel.tanch]

Hi Mark,

So for 2960 access and trunk port, it will be better to use dscp instead of cos, am I right? As for 3850 what is the other method if not using class maps and policies map. Able to give an example, thanks. 

[Mark Malone]

I do use DSCP an it works fine you can even capture the span in Wireshark and see your markings as they leave each port to be sure nothings being altered , check the source is marking it too but most do now with DSCP , check the access port sees it passes it and the trunks also passes it up, most phones devices now all mark in DSCP so avoids th whole re-map thing with cos

for 3850s to honor DSCP you don't need to do anything like NX-OS software they are default trust status so its up to you if you want to use auto qos or not , with nothing enabled it should not change the DSCP markings or alter them coming from the 2960 , should just carry them through , I did test this on my own switches and the markings for EF were not changed as they passed .See when you introduce auto class-maps other traffic gets dumped into queues too so its a choice if you want that to happen or not , you will see when you enabled auto trust on ios-xe it built a whole set of maps and policies in global config , matching certain traffic , nows it pretty generic and works well too but you need to check it to make sure its not going to effect any of your other traffic too now its queueing just in case