QoS question

[katerina.dardoufa]

I have configured the following QoS commands:

class-map match-all CLASS-PREC-DLSW
match access-group name PREC-DLSW
match protocol snmp
match protocol telnet
!
!
policy-map POLICY-PREC-DLSW
class CLASS-PREC-DLSW
  set precedence 3

which are applied on the fa0/1 which is the connection to our MPLS provider.

interface FastEthernet0/1
description LINK TO MPLS
bandwidth 128
ip address xxxxx 255.255.255.252
ip tcp adjust-mss 1427
duplex auto
speed auto
crypto map map_getvpn
service-policy output POLICY-PREC-DLSW

My question is this: Since I am just doing marking do I have to also set the default class in the policy-map and do I have to set the max-reserved bandwidth on the fa0/1 in order to take full advantage of the configured bandwidth?

Thanks in advance,

Katerina

[cadet alain · Accepted solution]

Hi Katerina,

class-map match-all CLASS-PREC-DLSW
match access-group name PREC-DLSW
match protocol snmp
match protocol telnet

You have a match-all class-map so all conditions must be true to match but a packet can't be a telnet packet and a snmp packet at the same time.

So your traffic will get into class class-default.

My question is this: Since I am just doing marking do I have to also set  the default class in the policy-map and do I have to set the  max-reserved bandwidth on the fa0/1 in order to take full advantage of  the configured bandwidth?

Cisco recommends not messing with the max-reserved bandwidth because it could wreak havoc on the network.

If you don't want to do anything on it you don't need to explictitly set class-default in policy.

Regards.

[katerina.dardoufa]

OMG cadetalain!!!

You're right!!!! I hadn't noticed that! Thanks for pointing that out!

[Mohamed Sobair]

Hi,

You dont need to mark at the egress, you need to mark at the Ingress and your marking in the ip header is preserved (Providing you have an agreement with the MPLS provider).

According to Cisco QoS, classification and marking should be at the ingress, and applying your QoS policy at the egress.

* The Max-reserved-bandwidth command is used when you have queuing outbound and you would like to reserve more the 75% of the interface bandwidth (Or your staticly configured Interface Bandwidth), However , Cisco doesnt recommend changing the default max-reserved-bandwidth above 75% as the 25% is reserved for L2 Overhead.

* The default class if not configured manually , will be assigned a precedence of 1 by default, unless you need to mark it otherwise, then you have to manually configure it.

HTH

Mohamed

[cadet alain]

Hi mohamed,

If no default class is configured, then by default  the traffic that does not match any of the configured classes is flow  classified and given best-effort treatment.  this is taken from here  http://www.cisco.com/en/US/docs/ios/12_0t/12_0t5/feature/guide/cbwfq.html#wp25297

best-effort is precedence 1? isn't it precedence 0 instead?

Regards.

[Mohamed Sobair]

Yes, you are right

The best effort (class-default) is assigned precednce 0 by default.

Regards,

Mohamed

[katerina.dardoufa]

Mohamed,

I think I should mark on the egress of my router, because I am marking DLSW traffic, telnet and snmp which are generated by the router! I don't think that I have an option to mark it anywhere else.

Regards,

Katerina