is QOS working on Access layer switch

[mahesh18]

Hi all,

we have this config on Access layer switch

h run int gi1/1
Building configuration...

Current configuration : 247 bytes
!
interface GigabitEthernet1/1
switchport
switchport access vlan 399
switchport mode access
switchport voice vlan 400
no ip address
speed auto 10 100
mls qos trust cos *********************************************************************
no mdix auto
flowcontrol receive desired
spanning-tree portfast
end

when i run command

sh mls qos
  QoS is disabled globally

my question is ---

is there any type of QOS  working on this switch or interface gi1/1 even though command

mls qos trust cos is configured on interface.

thanks

mahesh

[Mark Yeates]

Mahesh,

QoS is not working on the switch. You have QoS globally disabled, and will need to enable it before the CoS values are trusted on Gi1/1. Depending on the switch type you will want to configure "mls qos" or "qos" in global configuration mode on your switch.

HTH,

Mark

[mahesh18]

Hi Mark,

thanks for reply.

it is 6509.

i check the distribution layer

h mls qos
  QoS is enabled globally
  Policy marking depends on port_trust
  QoS ip packet dscp rewrite enabled globally
  Input mode for GRE Tunnel is Pipe mode
  Input mode for MPLS is Pipe mode
QoS Trust state is CoS on the following interface
Gi1/4 Gi1/5 Gi1/6 Gi1/7 Gi1/8 Gi1/9 Gi1/10 Gi1/11 Gi1/12 Gi1/13
QoS Trust state is DSCP on the following interface
Gi1/2 Gi1/3
  Vlan or Portchannel(Multi-Earl) policies supported: Yes
  Egress policies supported: Yes

----- Module [5] -----
  QoS global counters:
    Total packets: 208008
    IP shortcut packets: 0
    Packets dropped by policing: 0
    IP packets with TOS changed by policing: 3
    IP packets with COS changed by policing: 30725
    Non-IP packets with COS changed by policing: 0
    MPLS packets with EXP changed by policing: 0

sh mls   qos   mod  2
  QoS is enabled globally
  Policy marking depends on port_trust
  QoS ip packet dscp rewrite enabled globally
  Input mode for GRE Tunnel is Pipe mode
  Input mode for MPLS is Pipe mode
QoS Trust state is CoS on the following interface
Gi1/4 Gi1/5 Gi1/6 Gi1/7 Gi1/8 Gi1/9 Gi1/10 Gi1/11 Gi1/12 Gi1/13
QoS Trust state is DSCP on the following interface
Gi1/2 Gi1/3
  Vlan or Portchannel(Multi-Earl) policies supported: Yes
  Egress policies supported: Yes

  QoS global counters:
    Total packets: 388508
    IP shortcut packets: 0
    Packets dropped by policing: 0
    IP packets with TOS changed by policing: 8
    IP packets with COS changed by policing: 66351
    Non-IP packets with COS changed by policing: 0
    MPLS packets with EXP changed by policing: 0

here is distributionlayer config

interface GigabitEthernet1/4
switchport
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 400/500
no ip address
udld port aggressive
mls qos trust cos
flowcontrol receive desired
spanning-tree portfast disable
end

[Mark Yeates · Accepted solution]

Mahesh,

This switch has your QoS markings trusted. As to if your QoS is "working" is dependant on your configured QoS policies. Please see the red output below:

sh mls qos
QoS is enabled globally
  Policy marking depends on port_trust
  QoS ip packet dscp rewrite enabled globally
  Input mode for GRE Tunnel is Pipe mode
  Input mode for MPLS is Pipe mode
QoS Trust state is CoS on the following interface
Gi1/4 Gi1/5 Gi1/6 Gi1/7 Gi1/8 Gi1/9 Gi1/10 Gi1/11 Gi1/12 Gi1/13
QoS Trust state is DSCP on the following interface
Gi1/2 Gi1/3
  Vlan or Portchannel(Multi-Earl) policies supported: Yes
  Egress policies supported: Yes

----- Module [5] -----
  QoS global counters:
    Total packets: 208008
    IP shortcut packets: 0
    Packets dropped by policing: 0
    IP packets with TOS changed by policing: 3
    IP packets with COS changed by policing: 30725
    Non-IP packets with COS changed by policing: 0
    MPLS packets with EXP changed by policing: 0

Mark

[mahesh18]

hi Mark,

thanks for reply.

one last thing by best practice qos should be config on distribution layer not access layer?

[Mark Yeates · Accepted solution]

Correct. You should always classify or mark your traffic as close to the source as possible (Access layer). Your distro/core is where your policies should be placed. Your design would dictate exactly how and where. Below is a link to the Cisco QoS SRND guide. It is a good read especially in the campus QoS design area.

www.cisco.com/univercd/cc/td/doc/solution/esm/qossrnd.pdf

Mark

[mahesh18]

Hi Mark,

many thanks for the help you provided.

mahesh

[Mark Yeates]

Not a problem. Glad I could help!

Best of luck!

Mark