[cisco-voip] Trusting CoS on router uplink from switch...

Jonathan Charles jonvoip at gmail.com
Wed Jul 23 12:32:39 EDT 2008


Cos is recommended (per the QoS SRND) for any dot1q trunk...

However, my concern is not the switch, but the voice gateway's Fast
Ethernet to the switch... Do we need to trust outbound (switch to
gateway), and inbound (on the gateway side...)



Jonathan

On Wed, Jul 23, 2008 at 11:28 AM,  <Thorsten.Mayr at barclayscapital.com> wrote:
> Someone correct me if wrong and might actually depend on IOS and type of
> kit as well.
>
> As long as you don't have mls configured at all, you won't be rewriting
> the DSCP fields.
> If you have mls configured, you'll have to trust COS or DSCP whatever
> you prefer otherwise you'll overwrite with default value.
>
> I am not sure if it's better to trust on DSCP or COS in this case, If
> you are trunking you might as well stick to COS. Also you'll have wrr or
> srr queues setup which will map to COS.
>
> Haven't touched qos for a while and seems like I do have to freshen up
> on this topic ;)
>
>> -----Original Message-----
>> From: Jonathan Charles [mailto:jonvoip at gmail.com]
>> Sent: Wednesday, July 23, 2008 5:18 PM
>> To: Mayr, Thorsten: IT (LDN)
>> Cc: cisco voip; OSL CCIE Voice Lab Exam
>> Subject: Re: [cisco-voip] Trusting CoS on router uplink from switch...
>>
>> Well, I do have subinterfaces and it is a dot1q trunk to the
>> gateway... just looking for a config to trust the CoS and
>> DSCP... or wondering if the router will clear the DSCP and CoS....
>>
>>
>>
>> Jonathan
>>
>> On Wed, Jul 23, 2008 at 9:38 AM,
>> <Thorsten.Mayr at barclayscapital.com> wrote:
>> > Charles,
>> > You won't have COS on the link to the gateway as you won't have a
>> > dot1.q/isl tag, unless you use subinterfaces on the router.
>> >
>> > I'd trusting on DSCP in that case.
>> >
>> > Did I get this one right, now? ;)
>> >
>> > T
>> >
>> >> -----Original Message-----
>> >> From: cisco-voip-bounces at puck.nether.net
>> >> [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Jonathan
>> >> Charles
>> >> Sent: Wednesday, July 23, 2008 2:58 PM
>> >> To: cisco voip; OSL CCIE Voice Lab Exam
>> >> Subject: [cisco-voip] Trusting CoS on router uplink from switch...
>> >>
>> >> OK, so we set the switch ports to trust CoS on the dot1q
>> trunk from
>> >> phone to switch... are these then trusted from that point
>> on, or do
>> >> we need to trust them elsewhere as well?
>> >>
>> >> Do we need to add any config to the voice gateways to
>> trust the CoS
>> >> coming from the switches?
>> >>
>> >>
>> >>
>> >>
>> >> Jonathan
>> >> _______________________________________________
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>> >> cisco-voip at puck.nether.net
>> >> https://puck.nether.net/mailman/listinfo/cisco-voip
>> >>
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