Tarrfic-shape or Policy-Map

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Nov 25th, 2008
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Hi Experts! I am trying to configure bandwidth control (only ICMP) in a ROUTER but in "both" ways. From PCA to PCB I want to configure 200K, and from PCB to PCA I want to configure 400K. This configurations are done because I want to avoid excessive traffic that can be increase the process of my router. There is other kind of traffic passing through these interfaces must not controlled:

PCA ----> G1/1 ROUTER G2/2 ----> PCB

PCA <---- G1/1 ROUTER G2/2 <---- PCB

1.- What is better? traffic-shape or policy-map?

2.- If I use traffic-shape, in wich interface do I must apply?

3.- If I use policy-map, in wich interface do I must apply?

4.- Is the following configuration correct?


access-list 110 remark LIMIT PCA to PCB

access-list 110 permit udp host host eq snmp

interface G2/2

traffic-shape group 110 200000

access-list 120 remark LIMIT PCB to PCA

access-list 110 permit udp host host eq snmp

interface G1/1

traffic-shape group 120 300000

Normally, traffic-shape is used in the outside of the interface, but with this, there is passing a lot of traffic to the router. With "policy-map" is more efficient? Can you send me an example please?

Thanks for your help!!!

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Istvan_Rabai Tue, 11/25/2008 - 12:24
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Hi Carlos,

Traffic-shaping can be implemented in the outbound direction only.

So you must configure traffic-shaping on G1/1 and on G2/2 as well, if you want to implement it in both traffic directions.

The policy-map configuration is the newest method of configuring QoS.

Personally I would prefer to use the policy-map method, because it always separates traffic classification from the action taken on the traffic class, and this creates a more structured and clear configuration.

In addition to this, class-maps and policy-maps, once created, can be reused in other QoS configurations within the same router, which makes configuration quicker and the probability of configuration errors decreases.



carloskuontay Tue, 11/25/2008 - 13:08
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Thanks Istvan! Do you have an example of the configuration of policy-map?

Istvan_Rabai Tue, 11/25/2008 - 19:03
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Hi Carlos,


access-list 110 permit udp host host eq snmp

access-list 120 permit udp host host eq snmp

Classifying traffic:

class-map PCA-TO-PCB

access-group 110

class-map PCB-TO-PCA

access-group 120

Definition of QoS actions:

policy-map PCA-TO-PCB

class PCA-TO-PCB

shape average 200000

policy-map PCB-TO-PCA

class PCB-TO-PCA

shape average 300000

Applying QoS policies to the interfaces (in this case in the outbound direction):

interface Gig2/2

service-policy output PCA-TO-PCB

interface Gig1/1

service-policy output PCB-TO-PCA




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