08-12-2010 09:26 AM - edited 03-01-2019 02:20 PM
i came to an example where there is a following config:
policy-map TEST
class class1
bandwidth 128
shape average 256
class class-default
fair-queue
i remember that bandwidth set the minimum bandwidth, while police/shape set the maximum bandwidth for the class.
in this example, i know that the policy reserve 128 for class1.
if the BW exceed 128, the traffic goes to class-default and never "hit" the shape command....
i cant seem to figure how the shape command help here. as far as i know, bandwidth and shape/police should have the same value.
otherwise i really cant understand this configuration.
any1 have a clue?
08-15-2010 07:30 AM
Hello Arnon,
>> if the BW exceed 128, the traffic goes to class-default and never "hit" the shape command....
this is not correct, traffic classified in the class is in the class this is not a policer but a policy-map
This configuration provides a minimum of 128 kbps when the link is full to a maximum of 256 kbps to IP flows classified in this traffic class
without the shape command if no traffic is present on other traffic classes, the only upper limit is the interface speed (true or the result of a shaper in hierarchical QoS)
setting shape command to the same value of bandwidth makes minimum= maximum that is removes elasticity from CBWFQ
Hope to help
Giuseppe
08-15-2010 10:28 AM
>> if the BW exceed 128, the traffic goes to class-default and never "hit" the shape command...
actually it is correct. i a class exceed its given BW, the rest of the traffic is handled by class default.
i found the answer yesterday....
the shaper was configured for cases where there is no congestion (thus bandwidth command does not take effect) and we want to limit the class.
08-16-2010 02:28 PM
Hello Arnon,
>> actually it is correct. i a class exceed its given BW, the rest of the traffic is handled by class default.
not in my experience at least on high end devices like C7500 or 12000 I never see this to happen
and also according to Documentation
>> The default class of the policy map (commonly known as the class-default class) is the class to which traffic is directed if that traffic does not satisfy the match criteria of other classes whose policy is defined in the policy map
Hope to help
Giuseppe
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide