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QoS config / check

Level 1
Level 1

Can someone verify my config, trying to deploy QoS not because we need it, as utilization of my uplink interface's are 2%, but someone told my boss to do so because they don't want to trouble shoot on the server side, i am running a 3750g switch. We do not trunk the uplink currently, so my configuration will be supper basic i am just trying to give priority to incoming traffic on the uplink port listed on the local switch, the traffic is confined to just this one switch. All so will denfineing traffic based on ip address only, work, ex any traffic for x x x x address, give priority for any traffic to this address? I can probably figure out the config, if you can tell me it can be done. Gi 1/0/24 is the uplink     


Distribution1(config-std-nacl)#ip access-list extended DATA-Traffic

Distribution1(config-ext-nacl)#permit tcp any any eq 10668

Distribution1(config-ext-nacl)#permit tcp any any eq 10669

Distribution1(config-ext-nacl)#permit tcp any any eq 10670

Distribution1(config-ext-nacl)#permit tcp any any eq 10671

Distribution1(config)#class-map  Class-A

Distribution1(config-cmap)#match access-group name DATA-Traffic

Distribution1(config-cmap)exit Distribution1(config)#policy-map sample-policy1

Distribution1(config-pmap)#class Class-A

Distribution1(config-pmap-c)#set dscp af21


Distribution1(config)#interface gigabitEthernet 1/0/24

Distribution1(config-if)#switchport mode access

Distribution1(config-if)#service-policy input sample-policy1 Distribution1(config-if)#exit

3 Replies 3


Couple of my inputs...

First you configuration seems correct till the point that you are just marking the data with AF21. Just marking the data is not enough to provide QoS. Somewhere in your network ( generally the nodes, where there is congestion; you have to match those marking and provide desired action ( either priority, bandwidth, shape or police).

Secondly, as you mentioned that you are not overutilizing the capacity; even if you provide bandwidth, it won't come affect.

Just to sum it all:

QoS consist of :

1. Marking: Generally done at point close to source

2. Classification: Generally at access layer

3. Action: Can be priotrity ( generally used for Voice traffic), Bandwidth, Police and Shape.

In conjuction with your scenario, probably you should use bandwidth. However there is a catch that it will provide minimum defined bandwidth during the congestion time only; if there is no congestion it can use all the available bandwidth.



PS: Please rate helpful posts.

i am little confused as when i try to apply an action the only thing i can configure is police, unless i am doing something wrong, it is a 3750 switch, with an ip base 12.225 SE ios, is there anything i can do to take action besides police(see below output)? also do i need to do anything to the server interface? i was confused on the #mls qos trust dscp, is command used on the uplinks, i am not trunking and there is only 2 switches in my config, is this where i would apply this statement


QoS policy-map class configuration commands:

  exit            Exit from QoS class action configuration mode

   no              Negate or set default values of a command

   police          Police

  service-policy  Configure QoS Service Policy

   set            Set QoS values 

trust          Set trust value for the class 

all right i did some research, marking and policing are the only actions that can be taken on a 3750, (PHB) and i really do not want to alter the queuing. if is only mark the traffic with a EF46, will this command alone be able to give it priority in the que? And Thus accomplish the goal.

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