packet marking in cisco 7604 with PFC

Unanswered Question
Apr 29th, 2010
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Hi All:

I have this design issue .I have attached a diagram for reference.

There are GRE tunnels between two locations.

  These tunnels are transport over a parent GRE tunnel  – carrier GRE


4.       The carrier tunnel is terminating on the cisco 7604 and the carrier GRE packet getting de-capsulated on the 7604 and passenger GREs are going out to remote locations via egress interfaces.

6.       We need to ensure qos treatment for this de-encapsulated  traffic going out via egress interface.

7.       In a non 7600 platform, we can  use qos-group to identify these traffic at ingress of  and match the  qos-group group-id

at    At the egress of qos policy we can match this qos group and set a bandwidth for this group of traffic.

8.       But it seems 7604 is not supporting matching qos-group. How to solve this issue as now in Cisco 7604 there are lot of restrictons on usage of match qos-group in addition we are not sure how to set a dscp  marker on the de-encapsulated packet. Kindly help.




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rahurao Thu, 04/29/2010 - 20:58
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Hi Kaustav,

As per the description i can see that you are using a 7604 which is basically similar to a 6500. The QOS as configured on 7600 is pretty different as it is based upon hardware.

The 7600 have to treat hardware switcheed traffic as well as software switched traffic so the QOS is based upon the hardware queues here.

As a suggestion if you are using a software based QOS like using a QOS group it will not be able to understand it but we can use the software switched traffic to trust the COS markings and send it over to 7600 so the 7600 would be able to understand the same and will be able to honour the cos markings cominmg along with the packets.

For reference:

kaustav.gupta Thu, 04/29/2010 - 21:33
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Hi Rahul.

Thanks for your reply. Do you see any workaround to this design issue from the Cisco 7604 platform perspective.

rahurao Fri, 04/30/2010 - 01:58
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Hi Kaustav,

as we are concerned about the 7600 platform it should undrstand and respect the cos markings coming along with the packet.

From the router you need to make sure that it should send cos value tagged along with the packet and on the interface connected on the 7600 you can use mls trust cos so that the 7600 can understand the same and give the required priority.

The trust state of an ingress port determines how the port marks,  schedules, and classifies received Layer 2 frames, and whether or not  congestion avoidance is implemented. These are the port trust states:

Untrusted (default)

Trust IP precedence

Trust DSCP

Trust CoS

Please look at the follwoing confioguration guide for the 7600 for more reference:

Cisco 7600 Series Cisco IOS Software  Configuration Guide

I hope this helps!

Rahul K Rao

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