From: chrlewis@cisco.com
Date: Thu Sep 15 2005 - 10:59:13 GMT-3
Consider the following:
Traffic classified in class cos gets a cos value of 5
What does this mean?
If the traffic coming in is not tagged with a .1q or ISL header what
relevance does this have?
The CoS value is actually determined by the internal DSCP value, so you
need to determine how that internal DSCP is set.
With wrr-queue cos-map 1 5 you are sending cos 5 (derived from internal
DSCP) in to queue 1.
With wrr-queue bandwidth you are giving 1/91 parts of the bandwidth with
queue 1, is this what you want?
As a further exercise, are you clear on how you would configure priority
queueing for a different CoS on top of this?
Good show commands to become familiar with are
Show wrr-queue bandwidth
Show wrr-queue cos-map
And for extra credit know show mls qos map dscp-cos, this becomes useful
when you have to configure the switch to set egress cos to a non-default
value based off internal DSCP.
Chris
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Ahmed Ossama
Sent: Thursday, September 15, 2005 5:31 AM
To: ccielab@groupstudy.com
Subject: CAT 3550 switch again
Dear All,
I am confused about some quality of service principles.
1st If I want to give ICMP traffic the higher priority ( for example), I
have 3550 switch, the ingress port is fast 0/2 and the egress port fast
0/1.
Shall I match the input packets with policy map then set the cos to 5
then using wrr-queue bandwidth 1 30 30 30, wrr-queue cos-map 1 5
Configuration will be as follow:
interface FastEthernet0/1
switchport access vlan 3
switchport mode access
no ip address
wrr-queue bandwidth 1 30 30 30
wrr-queue cos-map 1 5
wrr-queue cos-map 2 1 2
wrr-queue cos-map 3 0 3 4 6
wrr-queue cos-map 4 7
spanning-tree portfast
!
interface FastEthernet0/2
switchport access vlan 3
switchport mode access
no ip address
service-policy input cos
end
!
Switch#sh policy-map cos
Policy Map cos
class cos
set cos 5
Or I must use a dscp -to-cos map and at the ingress set a dscp values as
shown:
interface FastEthernet0/2
switchport access vlan 3
switchport mode access
no ip address
service-policy input cos
!
Switch#show policy-map cos
Policy Map cos
class cos
set ip dscp 5
!
mls qos map dscp-cos 45 to 5
Or the two solutions are valid.
Thanks ,
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