we use some Cat6500Sup720Base (Native-IOS 12.2.18SXD4) as router in the core. All interfaces of these devices are real Layer-3 (no VLAN-Interfaces).
Now we have to implement QoS. How is it possible to put received and transmit traffic to different queues (standard and priority) based on the DSCP-value?
We have currently configured:
no mls qos rewrite ip dscp
mls qos trust dscp
The modules in the chassis have a strict priority- and another queue (Rx1p1q4t Tx1p2q2t).
In all documentation that I found was no information about the mapping from IP-traffic to receive/transmit queues based on the received DSCP-value. I know how I can to this e.g. with the Cat3750 or Cat3560 platform.
All what I found was:
Mapping CoS Values to Tail-Drop Thresholds
Mapping CoS Values to Strict-Priority Queues
Mapping CoS Values to Standard Transmit-Queue Thresholds
Mapping CoS Values to Standard Receive-Queue Thresholds
I need exactly these steps, but based on DSCP. But because the devices are pure Layer-3, there are no dot1q-trunks and so also none CoS values.
Additionally I have these comments about your post:
- By disabling qos rewrite you are somewhat defeating the purpose of establishing trusted interfaces. I would suggest leaving qos rewrite enabled and continue defining trusted interface. By default, a trusted interface will not have its qos value remarked to 0 unless it is further defined in a policy to do so.
- On a Sup720 with PFC3, packets transmitting on trusted interface with DSCP values mapping to a COS of 5 will automatically be placed in the strict priortiy queue.
- Receive queue priorities are based on COS, so yes, pure Layer3 intefaces will not be available for special receive queuueing policies.
- You can assigin QoS marked traffic to queues and thresholds on transmit using 'wrr-queue' statements as defined in the attached document.
- Read the 6500 PFC QoS Configuration guide if you have not already.
"- On a Sup720 with PFC3, packets transmitting on trusted interface with DSCP values mapping to a COS of 5 will automatically be placed in the strict priortiy queue." If the linecard has a priority queue.
The key here is that we queue based on CoS value. Your DSCP->CoS mappings control the queueing of egress packets. From there, you can move CoS wherever you like and that is where the equivalant DSCP value will go. Since you trusted DSCP, you will map from DSCP->CoS for queueing. On the way out, you must make sure your CoS->DSCP maps mirror the DSCP->CoS maps so that you do not change the markings.
I also see you are looking to use "no mls qos rewrite ip dscp" - this is fine, as long as you aren't planning on doing more marking on this switch. If you are strictly trusting and then queueing, you can get away with not worrying about the CoS->DSCP map, but you still need to map DSCP->CoS appropriately according to your queueing requirements.
"My question, does Sup720PFC support dscp to wrr queue&threshold? "
No. The DSCP value is mapped to COS to decided queue and threshold placements. This is more of a factor/limitation of the Catalyst line cards than it is with Sup720.
IOS routers are capable of DSCP based WRED drop thresholds and queue assignments.
I suggest reading the Enterprise QoS Reference Network Design Guide, and PFC QoS Configuration Guide that I link to in my first post for this thread. These are excellent reads that cover all of the details discussed here.
This is actually a pretty cool feature, i didn't even know it existed until I was looking for a solution to advertise a subnet (prefix in BGP talk), only if a certain condition existed. This is exactly what conditional advertisements does
j ai une question j ai achete un routeur cisco 887VA-k9 , je le configuré avec la configuration ci- dessous
si je le lier avec mon pc portable sur l un de ses ports directement ça marche toute est bien ( la connexion internet + m...
Attached policy provides CLI access to the Cisco 4G router over text messaging. Two files are in the attached .tar file:
2. PDF with instructions on how to load and use the .tcl file.