From: Chris Lewis (chrlewiscsco@yahoo.com)
Date: Mon Nov 21 2005 - 17:34:54 GMT-3
Yes Venkat, agreed, I have re-posted my answer to correct the reference to cos on an access port, and I hope it is clear how setting COS on ingress drives the precedence value on egress in the 3550 QoS mechanism.
Regards the wrr-queue reference, I believe your statements are correct.
"Venkataramanaiah.R" <vramanaiah@gmail.com> wrote:
Chris, thanks for jumping in and clarifying..
A) I agree with you on item #2. I was wrong in my understanding.
However, for #1, we did some tests and found that we can set cos and
in turn dscp on access ports as well..
From our tests, we see that it is not that access/trunk which sets the
cos/dscp but the combination of commands..
The following combination seem to be setting these values,
irrespective of the switchport mode.
a) mls qos cos 3 and mls qos cos override
b) mls qos cos 3 and mls qos cos trust
This effectively means that you can explicitly specify either to trust
the COS values or override them. Just the mls qos cos 3 command does
not seem to do anything w/o these additional commands. Hope you
agree..
B) I also have this question from the archive link that you provided.
Regarding the wrr-queue bw calculation, You have mentioned in Cisco
example, that priority queue takes 1/101 share because Q4 is
configured with weight 1. But my understanding is that, if
priority-queue out is configured then the Q4 weight value is not
included in the bw calculation formula. So effectively what i mean is
that Q4 does not get any share as such, but it is serviced before
giving any share to other queues.. Is this correct?
Regards
-Venkat
On 11/21/05, Chris Lewis wrote:
> Venkat,
>
> The methodology used at
> http://www.groupstudy.com/archives/ccielab/200509/msg00464.html
> can help in verifying all these things. Here is what I did to verify these
> questions.
>
> R1--SWA--R2
>
> R1 (10.1.1.1) can ping R2 (10.1.1.2)
>
> I configure the Switch and check its cos to internal DSCP mapping as
> follows:
>
> SW-A#sho mls qos maps cos
> Cos-dscp map:
> cos: 0 1 2 3 4 5 6 7
> --------------------------------
> dscp: 0 8 16 24 32 40 48 56
>
> mls qos
> !
> interface FastEthernet0/1
> switchport mode access
> mls qos cos 3
>
> At this stage R1 can ping R2, now I apply the following ACL inbound on R2
>
> access-list 100 permit icmp any any prec 3
>
> This is now what happens on R1
>
> R1(config-if)#do ping 10.1.1.2
> Type escape sequence to abort.
> Sending 5, 100-byte ICMP Echos to 10.1.1.2, timeout is 2 seconds:
> U.U.U
>
> Now I add the following to the switch on the interface connecting to R1
>
> SW-A(config-if)#switch trunk encap dot1q
> SW-A(config-if)#switch trunk nat vlan 1
> SW-A(config-if)#switch mode trunk
>
> R1 still cannot ping R2. I now add the last piece to the switch interface
> connecting to R1
>
> SW-A(config-if)#mls qos trust cos
>
> And the ping is replied, R1 is now able to ping R2 successfully again.
>
> The key here is in understanding what you have to do to set the internal
> DSCP and how that is used on egress by the switch.
>
> So in summary both 1 and 2 are incorrect..
>
> Chris
>
>
> "Venkataramanaiah.R" wrote:
> Sorry for catching up late on this thread, but just wanted to clarifiy
> 2 things here, because someone might read this archive later..
>
> 1) mls qos cos 3 can work in access port
>
> 2) mls qos cos does not set the precendence..
>
> Please correct if i am wrong..
>
> -V
>
> On 11/15/05, Niche wrote:
> > Hi there,
> >
> > "mls qos cos 3" will not kick-in cause your port is not a trunk port (and
> I
> > assume that port is not connecting to a 7960). You can use class-default
> for
> > marking remaining traffic to precedence 3.
> >
> > Cheers~
> > Jacky
> >
> > On 11/15/05, Daniel Berlinski wrote:
> > >
> > > Hi everyone.
> > >
> > > Will the following configs mark HTTP traffic coming from vlan 12 with
> > > precedence 5 and mark the remaining traffic with precedence 3?
> > >
> > >
> > >
> >
> -----------------------------------------------------------------------------
> > ---------------------------------------------
> > > mls qos
> > > access-list 170 permit tcp any any eq www
> > >
> > > class-map match-any HTTP
> > > match access-group 170
> > > class-map match-all VLAN12
> > > match vlan 12
> > > match class-map HTTP
> > >
> > > policy-map MARKING
> > > class VLAN12
> > > set ip precedence 5
> > >
> > > interface FastEthernet0/2
> > > switchport access vlan 12
> > > switchport mode access
> > > mls qos cos 3
> > > service-policy input MARKING
> > >
> > > Rack1SW1#sh mls qos inter fa0/2
> > > FastEthernet0/2
> > > Attached policy-map for Ingress: MARKING
> > > trust state: not trusted
> > > trust mode: not trusted
> > > COS override: dis
> > > default COS: 3
> > > DSCP Mutation Map: Default DSCP Mutation Map
> > > trust device: none
> > >
> > >
> >
> -----------------------------------------------------------------------------
> >
> ------------------------------------------------------------------
> > >
> > > From the documentation CD: "You cannot configure both port-based
> > > classification and VLAN-based classification at the same time. When you
> > > configure the match vlan vlan-list command, the class map becomes
> per-port
> > > per-VLAN based. If you configure a policy map that contains both
> port-based
> > > and VLAN-based class maps, the switch rejects the policy map when you
> > attach
> > > it to an interface"
> > >
> > > Will "mls qos cos 3" under the interface mark the remaining traffic with
> > > precedence 3?
> > >
> > > Best regards
> > >
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