Ip Precedence remarking

[alk1000]

Hi All,

I just have a quick question.

As everyone knows, Cisco systems reserve the ip precedence 6 and 7 to internet and network respectively. http://www.cisco.com/en/US/products/sw/iosswrel/ps1828/products_configuration_guide_chapter09186a00800ca58f.html

My question is, can we remark these 2 classes, i.e. can we assign ip precedence 4 to the internet and 3 to network traffic?

Any link is welcomed

Thanks and regards,

Daniel

[pkhatri]

Hi Daniel,

Are you interested in re-marking traffic locally generated by the router itself ?

The names that you are using for the precedence values are very much out-dated and 'internet' does not really mean Internet traffic. In fact, Cisco routers assign a precedence of 6 to management traffic such as OSPF packets etc.

You can apply service-policies to match on such packets and drop the precedence down but I don't think that's what you want....

Hope that helps - pls rate the post if it does.

Paresh

[alk1000]

Hi Paresh,

Thanks for your reply. I am aware that the internet class is not the real internet traffic. But I followed the naming in use by Cisco documentation - please see the link attached.

I am interested in remarking those two ip precedence (6 and 7). Is it possible?

Ps: I know the method to classify traffic and remark it.

[mheusinger]

Hello,

in principle you could, but be aware that this means usually router generated traffic, which is mostly routing updates. Except maybe BGP those routing updates will be link local. There is no real gain in remarking those, because in this case only the router generating the marked traffic will need to prioritize.

Still you can remark those packets with a local policy: "ip local-policy route-map NMS" and a route-map setting ip precedence to the desired values.

I´d also like to note, that the terms internet (prec 6) and network (prec 7) are not Cisco proprietary but defined in the respective RFC.

What is the underlying problem you like to solve?

Hope this helps! Please rate all posts.

Regards, Martin

[pkhatri]

As Martin pointed, you can certainly re-mark these precedence values to whatever you want using the normal method of classification and marking using MQC.

However, I would like to understand your reasons for wanting to do so... it's not something that is done in practice, that's all.

Paresh

[alk1000]

Hi Martin,

Tanks for your reply.

Do you have any links backing up you response. I am interested so I can prove it to a colleague.

I raised this question as part of QOS config troubleshooting. As per below policy map:

policy-map MARKING

class GOLD-RT-SET

set ip precedence 5

class GOLD-SET

set ip precedence 4

class SILVER-SET

set ip precedence 3

class BRONZE-SET

set ip precedence 0

class class-default

set ip precedence 0

There is an access-list for each class as following:

class GOLD-RT-SET is voice traffic

class GOLD-SET is Citrix traffic

class SILVER-SET is few other application traffic

class BRONZE-SET is ip any any (so all the traffic left other than the above)

Going back to the definition of the default class “Any traffic which does not belong to the any class in a policy-map”, I believe we’re accidentally remarking the 6 and 7 ip precedence to 0

Am I right in analysing it!

[bhedlund]

I think you will find your answers in this document:

http://www.cisco.com/application/pdf/en/us/guest/netsol/ns432/c649/ccmigration_09186a008049b062.pdf

I would like to echo the thoughts of the other distinguished posters here in that remarking internetwork protocol traffic is not only uncommon but just a bad idea all together.

If you remark your routing protocol traffic in the same catagegory as bulk and/or best effort traffic you put yourself in a much riskier position with little to no reward.

Please rate all helpful posts.

Regards,

Brad

[pkhatri]

Going back to what the original poster has said was configured, I would have to agree that in that case, all of the Prec 6 and 7 traffic would be getting re-marked to zero, since the policy-map is not explicitly catching any control traffic. As such, it will fall through to class-default and get marked with an IP precedence of zero !

Hope that helps - pls rate the post if it does.

Paresh