Catalyst 6500 and Class-based Qos

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Mar 28th, 2008
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I've been playing with nested cbQos several times on pure L3 devices.

My usual configuration use:

- parent policy, with general policer limiting bandwith per-vlan

- child policy, with percentage on NBAR matching

Now I wanted to use the same approach on my switched network:

- cat2960 as access-devices

- cat6500 sup720 as distribution/core ones

I've been setting a police/class on vlan, and specifying "mls qos per-vlan" on trunk port between access and core.

Although I see some improvement (flow is slowed), the expected police is not reached (e.g. set a "police 32000" and I get a 1Mbit of traffic, sustained)

Any suggestion, before leaving CBQOS and try to use Cos/DSCP?



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ibrunello Thu, 04/03/2008 - 10:27
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A good reading.

Will keep this as a reference.

Unfortunately, my 6500s are running Native-IOS, so I have to dig into the IOS equivalent commands.

Thank you

ibrunello Tue, 04/08/2008 - 03:23
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The CatOS version of the documentation seems a bit more clear than the Native one:

BTW, I managed to configure the policer in a CBQOS way, applying on VLAN:

1) (optional) mark packets at access switch, and set the trust mode on trunk poort

2) set an IP access-list on core.

I would put on a core, since I have several access switches on policed VLAN, and I want to make an aggregated L3 police.

3) set a class-map on core, matching ACL

4) set a policy map on core, matching class-map

5) apply policy map w/ the service-policy command.


- use "output" clause for inbound traffic directed to VLAN

- use "input" clause for outbound traffic coming from VLAN

this makes perfect sense if you think of VLAN just like a physical interface.

6) (optional) set qos vlan on trunk port coming from access-switches:

MLS01(config-if)# mls qos vlan-based


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