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New Member

mls qos question on 3845 router and traffic marking questions

Hi all,

I got a 3845 router which is running IPSec and QoS by service-policy which classifies all incoming traffic by IP precedence values. If I have a new requirement to handle the traffic of dscp 34(assume I have marked those interesting traffic at the access switch) and I want to preserve its dscp and sent them out with prioirty, will the following config work?

##############################

Partial config of existing 3845 router

##############################

class-map match-any Precedence1
match ip precedence 1
class-map match-any Precedence5
match ip precedence 5
class-map match-any Precedence3_4
match ip precedence 3
match ip precedence 4
class-map match-any Precedence6_7
match ip precedence 6
match ip precedence 7

policy-map QoS

class Precedence3_4

   priority percent 9
class Precedence1
  bandwidth percent 4
  random-detect

  ...

  ...

Q1) To handle the traffic with dscp 34, can I simply creat a new class map & new actions under policy-map, then re-map the IP precedence-to-DSCP below? And I don't need to enable "mls qos" globally in this case?

class-map match-any DSCP-34

match ip dscp 34

policy-map OutQoS

  class DSCP-34

   priority percent 10

mls qos map dscp-cos  32 33 35 36 37 38 39  <remove dscp 34 from ip precedence 4.>

Q2) On the 3560 switch that originates the traffic of interest, is it OK if I configure the followings to mark the traffic to dscp 34 like something below? Or should I keep the 3560 switch in L2 to mark the traffic instead?

ip routing

mls qos
access-list 100 permit ip any any
class-map match-all ANY
  match access-group 100
policy-map MarkDscp34
  class ANY
   set dscp af41
int fa1/0/X
service-policy input MarkDscp34
priority-queue out
mls qos trust dscp

Million thx in advance,
goku
3 REPLIES
New Member

Re: mls qos question on 3845 router and traffic marking question

Hi all,

Would anyone please with qos experience can share the experience or give me some hints to my queries..

Many thanks,

Goku

Silver

Re: mls qos question on 3845 router and traffic marking question

IOS routers don't use the command 'mls qos' nor do they have the concept of 'enabling QoS globally'.

Your new class map looks good. 

Keep in min that in CBWFQ there is only one priority queue.  Therefore when this class map is applied to the policy map it should use the keyword 'bandwidth percent' instead of 'priority percent'. 

If this traffic does indeed need access to the priority queue you should instead modify the 'class map Precedence3_4 to also match DSCP 34.  Then increase the percentage allocated for that class under the policy map.  Something like this:


class-map match-any Precedence3_4
match ip precedence 3
match ip precedence 4
match ip dscp 34
exit


policy-map QoS
class Precedence3_4
   priority percent 20
exit
exit



Chris

New Member

Re: mls qos question on 3845 router and traffic marking question

Thanks Chris for your reply.

However, if I need to define a single class of traffic (dscp 34)

Can I use the following command to remove dscp 34 from precedence 4(to make a class of precedence 3 & 4  and another class for dscp 34)

mls qos map dscp-cos  32 33 35 36 37 38 39

class-map match-any DSCP-34

match ip dscp 34

policy-map OutQoS

  class DSCP-34

   priority percent 10

Thanks,

Goku

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