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DSCP interoperability Procurve <> Cisco

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Jaap Laaij
Frequent Advisor

DSCP interoperability Procurve <> Cisco

Hi all,

We are on the brink to implement a VoIP solution. This includes the WAN.
On the LAN side on all locations is a 5400/5412 Procurve switch. On the WAN side there is a Cisco router type 1841 up to a ASR1002v2. The WAN routers are maintained by our provider.

I have heard there is a difference interpreting DSCP values bij HP versus Cisco.
Is this true? If so, is there any document on the differences?

Thanx Jaap
Pieter 't Hart
Honored Contributor

Re: DSCP interoperability Procurve <> Cisco

possibly this refers to implementing RFC4594.

Many vendors implemented QoS functionality before this RFC has been published.
This RFC changes some classifications and nomenclature.
But is a "best practice" not a requisite standard!

eg this recomendation exchanges Call signaling CS5/DSCP40 and Broadcast video CD3/DSCP24.

some vendors use this RFC by default, other vendors you may need to manually modify the COs to DSCP map to implement this RFC.
Antonio Milanese
Trusted Contributor

Re: DSCP interoperability Procurve <> Cisco


>have heard there is a difference interpreting DSCP values bij HP versus Cisco.
Is this true?

Do you mean DSCP to CoS mapping?

Some hp models (lowend or old ones i.e. 5300) have only four egress queues per port and accordingly usable" CoS priorities are effectively are halved and spreaded (mapped) on those queues. New models have 8configurable queues so CoS to queue mapping is 1:1.

You can choose to use/honore DSCP codepoints to/form up/downstream switches as a globally option

qos type-of-service diff-services

The default DSCP to CoS mapping table:

show qos dscp-map

is modifiable so you could change DSCP codepoint to CoS priority mapping using command:

qos dscp-map "DSCP_codepoint" priority "Cos_priority"

To display COS to queues/buffers mapping:

show qos queues-config

I suggest to read the traffic management manual of your model(s) since there are options (classifier-based Qos policies,qos marking,ecc.)

Cisco has a more advanced QoS options (in/out queue,schedulers ecc,autoqos,ecc.) but standard basic DSCP is working as expected.


Pieter 't Hart
Honored Contributor

Re: DSCP interoperability Procurve <> Cisco

more detail about the cisco implementation


Cisco has made a minor modification to its adoption of RFC 4594, namely the switching of Call-Signaling and Broadcast Video markings (to CS3 and CS5, respectively). A summary of Cisco's implementation of RFC 4594 is presented in Figure 2.

As Antonio explained you can query the current CoS to DSCP mapping and set a new mapping "to match the other side".

NB! it is possible that on the WAN link traffic is only differentiated by CoS value, not by DSCP! (so less granular)
Ask your provider about this.
Jaap Laaij
Frequent Advisor

Re: DSCP interoperability Procurve <> Cisco

Enough information to research our needs and discuss with our providers.

Thanks again guys ! :)