From: John Caronilli (jcaronilli@yahoo.com)
Date: Thu Dec 01 2005 - 19:07:13 GMT-3
Thanks Anthony,
How does the router know the arriving packet is
configured with a precedence bit and not already
configured with a DSCP value?
Also, isn't it a little sloppy to force every packet
through the switch to convert it's precedence to DSCP?
What if you had a port that you did not want to
convert the precedence bit?
It just seems the entire operation is not granular
enough?
John
--- Anthony Sequeira <terry.francona@gmail.com> wrote:
> Hi John!
>
> You cannot enter the command below on a 3550 without
> getting an error
> message! You need to actually provide the DSCP
> values that you want to
> assign based on the IP Precedence values of 0
> through 7. Here is an example
> of the full command syntax:
> *mls qos map ip-prec-dscp 10 15 20 25 30 35 40 45
> *
> Now - as far as how you apply it to an interface -
> the 3550 documentation
> states:
>
> "All the maps, except the DSCP-to-DSCP-mutation map,
> are globally defined
> and are applied to all ports.You can have multiple
> DSCP-to-DSCP-mutation
> maps and apply them to different Gigabit-capable
> Ethernet ports. However, on
> 10/100 Ethernet ports, you can attach only one
> DSCP-to-DSCP-mutation map to
> a group of twelve ports. "
>
> So, based on this, realize that you ip-prec-dscp map
> is automatically
> applied to all interfaces after you create it.
>
> Also - do not forget the command mls qos before you
> do anything with QoS
> manipulation on the 3550.
>
> Here is the documentation link I consulted and
> quoted:
>
>
http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12225sec/3550scg/swqos.htm#wp1150175
>
>
> On 12/1/05, John Caronilli <jcaronilli@yahoo.com>
> wrote:
> >
> > On the 3550, I configured the command:
> >
> > mls qos map ip-prec-dscp
> >
> > How is that command applied to an interface? How
> do
> > you tell the switch to convert all packets
> arriving on
> > say Fast 0/3 from the IP precedence value to DSCP
> > values?
> >
> > How does the switch know the arriving packet is
> not
> > already using DSCP?
> >
> > Thanks!
> >
> > John
> >
> >
> >
> >
> >
> > __________________________________
> > Start your day with Yahoo! - Make it your home
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>
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