Trust state in Nexus 7000

Question

Hi  According to the doc, by default, N7K trust dscp and CoS and preserve the value at ingress.  A packet traverse N5K which is trunked to N7K. The packet contains both DSCP and COS value. In such scenario,   (1) Will the N7K just use the COS value in the packet to perform egress queueing? Or it will use the DSCP value, then check against the default dscp-cos mapping table, and use that COS value to perform egress queueing?  The reason i asked is because if i have a scenario the packet consists of COS=4, DSCP=24, egress queuing (based on CoS) will be different. If N7K simply uses COS=4, then it will be mapped to Queue4 for example. If N7K uses DSCP=24, dscp-cos mapping maps to COS=3, then egress queuing will be maped to Queue3.  Any idea?  Eng Wee

Answer 1

Hi Andy,
I'm struggeling with QoS on a N7K (mixed F1 and M1 cards) and stumbled across your reply.
Assume that you've meant COS 0,1,2,3,4,5,6,7 in the rigth coloumn.
I need to classify, mark and queue IP-storage traffic (NFS and iSCSI) from a NetApp FAS, which cannot mark trafic (I've been told be NetApp).
Therefore I need to mark ("remark") the traffic to AF21/COS2 on the 802.1Q trunk (actually running as a VPC), from/towards the NetAPP, which is connected to an F132XP-15 port.
According to the manual I cannot do COS marking in ingress, but only DSCP.
My config :
ip access-list NetApp-storage
  10 permit ip 10.xxx.yyy.0/24 any    <-- used for NFS
  20 permit ip 10.xxx.zzz.0/24 any    <-- used for iSCSI
class-map type qos match-all IPstorage-IN
  match access-group name NetApp-storage
policy-map type qos NetApp-IN
  class IPstorage-IN
    set dscp 18
  class class-default
    set dscp 0
int po xxx                                     <--- VPC towards NetApp FAS
  service-policy type qos input NetApp-IN
So based on your comments the "storage" traffic will exit the switch with COS=0 - correct ?
In order to set the COS properly upon egress, I would need to additional configure :
policy-map type qos NetApp-OUT
  class IPstorage-IN
    set cos 2
  class class-default
    set Cos 0
int eth xx/yy or port-channel zzz              <--- ports towards "storage users"
  service-policy type qos output NetApp-OUT
on all ports ???
So based on your comments the "storage" traffic will exit the switch with COS=0 - correct ?
In order to set the COS properly upon egress, I would need to additional configure :
policy-map type qos NetApp-OUT
  class IPstorage-IN
    set cos 2
  class class-default
    set Cos 0
int eth xx/yy or port-channel zzz              <--- ports towards "storage users"
  service-policy type qos output NetApp-OUT
on all ports ???
Additional queueing questions :
Will the egress queing be done correctly, by only setting the DSCP upon ingress ?
My config :
qos copy policy type queuing default-4q-8e-out-policy prefix QQ_
policy-map type queuing QQ_4q-8e-out
  class type queuing 1p3q1t-8e-out-pq1
    priority level 1
  class type queuing 1p3q1t-8e-out-q2
    bandwidth remaining percent 1
  class type queuing 1p3q1t-8e-out-q3    <--- COS 2 should go here
    bandwidth remaining percent 49
  class type queuing 1p3q1t-8e-out-q-default
    bandwidth remaining percent 50
int eth xx/yy or port-channel zzz              <--- ports towards "storage users"
  service-policy type queuing output QQ_4q-8e-out
  service-policy type qos output NetApp-OUT
Is this correct ?
Best Regards
Finn Poulsen