Catalyst 3850 auto QOS command automatically modified

[oguarisco]

Hi all,

I was configuring a 3850-24 inserting the IOS command under an uplink interface to trust the CoS: " auto qos voip trust"
and I found out that the switch modify the command inserting into the port config:"auto qos trust"

Is this a normal behaviour? Checking the 3850 IOS XE configuration guide it state that both "auto qos voip trust" and auto qos trust" are  configurable...so why do the switch automatically change the QoS Command?

Morevoer the "auto qos trust" have 3 subcommand:

• none (default)
• cos
• dscp

If I configure "auto qos trust" will automatically trust both DSCP and CoS settings on the trusted port?

Any feedback are appreciated

O.G.

[Mark Malone · Accepted solution]

Hey You don't actually have to set that on an interface on a 3850 , by default they are set to already trust the dscp that a phone would send in

you can if you like set it and you should always try set to dscp , covers both l2 & l3, cos gets put in l2 header and usually gets remapped by the switch anyway to dscp

as below one of my 3850s no qos applied but carrying the markings from my other switches for voice in dscp 46 , it does not automatically cover egress so you should still apply it outbound although I haven't had an issue of it removing markings either , you can test easy enough with a wireshark

I was going to configure mine before I came across that and confirmed it with TAC to be sure so I just left them in the end as all I wanted was to make sure my voice and video markings were being carried

3850#show platform qos dscp-cos counters gigabitEthernet 1/0/1
Ingress DSCP0 9379231267    0
Ingress DSCP1 364402        0
Ingress DSCP2 22435767      0
Ingress DSCP3 622           0
Ingress DSCP4 16624441      0
Ingress DSCP5 0             0
Ingress DSCP6 0             0
Ingress DSCP7 0             0
Ingress DSCP8 42462464      0
Ingress DSCP9 0             0
Ingress DSCP10 1775841215    0
Ingress DSCP11 0             0
Ingress DSCP12 0             0
Ingress DSCP13 0             0
Ingress DSCP14 0             0
Ingress DSCP15 0             0
Ingress DSCP16 13757500      0
Ingress DSCP17 0             0
Ingress DSCP18 427563936     0
Ingress DSCP19 0             0
Ingress DSCP20 0             0
Ingress DSCP21 0             0
Ingress DSCP22 0             0
Ingress DSCP23 0             0
Ingress DSCP24 2298174       0
Ingress DSCP25 17            0
Ingress DSCP26 188243122     0
Ingress DSCP27 0             0
Ingress DSCP28 0             0
Ingress DSCP29 0             0
Ingress DSCP30 0             0
Ingress DSCP31 0             0
Ingress DSCP32 564189        0
Ingress DSCP33 0             0
Ingress DSCP34 25946655      0
Ingress DSCP35 0             0
Ingress DSCP36 0             0
Ingress DSCP37 0             0
Ingress DSCP38 0             0
Ingress DSCP39 0             0
Ingress DSCP40 6586045       0
Ingress DSCP41 0             0
Ingress DSCP42 0             0
Ingress DSCP43 0             0
Ingress DSCP44 0             0
Ingress DSCP45 0             0
Ingress DSCP46 152901577     0