From: Styran (styran@gmail.com)
Date: Thu Mar 12 2009 - 10:06:01 ARST
Hi Richard,
If you're applying the service-policy command under the tunnel interface,
you dont need to add the qos-preclassify under the tunnel interface. IOS
copies the DS-Field or TOS byte of the original IP header to the new the IP
header ( eg: in case of GRE tunnel, when the original packet is
encapsulated), so intermediate nodes can examine this field to apply
appropriate QOS policies.
As to when to use the qos-preclassify, I believe this might help
*
http://ccieeverest.blogspot.com/2008/12/qos-pre-classify.html
Lejoe*
On Thu, Mar 12, 2009 at 9:52 PM, Hunt, Richard (LDN-GIS) <
Richard.Hunt@interpublic.com> wrote:
> Dear All,
>
> I have backup WAN over a provider MPLS that uses GRE tunnels (but it's just
> a
> network with GREs nothing complex). It's hub and spoke in essence. I have
> a
> service-policy that matches my VoIP traffic and is applied to each Tunnel
> interface. As far as I could determine it was all marking and sending the
> VoIP using LLQ ( I used Netflow to verify this). Now I read about the
> 'pre-classify' interface command and I'm a little confused as to whether my
> receiving tunnel interfaces are able to pass on the original QoS marking
> (based on DSCP) and therefore if the rest of the LAN behind can prioritise
> this traffic.
>
> My GRE tunnel service-policy is applied outbound on all sites including the
> hub site and that seems to give priority based on my match criteria.
> Here's the CCO link that has me confused.
>
> http://www.cisco.com/en/US/tech/tk543/tk545/technologies_tech_note09186a00801
> 7405e.shtml#qoscomm<http://www.cisco.com/en/US/tech/tk543/tk545/technologies_tech_note09186a00801%0A7405e.shtml#qoscomm>
>
> Can anyone shed any light, has anyone sniffed this on say a LAN Ethernet of
> a
> router that has a GRE to another site? Who knows when you'd use
> 'pre-classify'?
>
> Thanks in advance.
> Richard.
>
>
>
>
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