06-24-2019 09:09 PM
Hello,
I have two switches (L3), one at site A and one at site B, between them is a WAN link that is not QoS aware but has dedicated bandwidth, so all I need to do is order my packets appropriately.
My application tags my traffic already, all I want to do is prioritise the traffic so i send the higher priority out before the lower priority.
I understand on my input interfaces I just run this command: "mls qos trust dscp"
what command do I run on the WAN interface? if I run the same command (trust dscp) will the interface actually send the packets in order of priority or just persevere the tags?
06-24-2019 10:14 PM
Hello,
which switch models do you have, and what Ios versions are you running ?
06-24-2019 10:44 PM
sorry yes that would have helped.
Its 3750X, v12.2(55) on site A, site B is 3850 03.07.04e
07-09-2019 03:37 PM
Anyone ale to assist with this? Was hoping its pretty simple
07-10-2019 01:21 AM
Hello,
on the 3750X you typically use SRR. Each interface has 4 queues, and the default queue to DSCP mappings are:
Queue 1: DSCP 40 to 47
Queue 2: DSCP 0 to 16
Queue 3: DSCP 16 to 31
Queue 4: DSCP 32 to 39, 48 to 63
You can assign different bandwidth weights to each queue.e.g.:
srr-queue bandwidth shape 40 20 20 20
If you know exactly which DSCP values need priority, you can map the weights accordingly. I would suggest to configure the below on the WAN interface of your 3750X:
interface GigabitEthernet0/0
description WAN Link to 3850
srr-queue bandwidth shape 40 20 20 20
priority-queue out
The 'priority-queue out' simply means that queue 1 is always served first.
On the 3850, you could use something like the example below:
policy-map SHAPE_WAN
class-map DSCP
match dscp ef af41
shape average percent 50
class class-default
bandwidth remaining 50
fair-queue
!
interface GigabitEthernet0/0
description WAN Link to 3750X
service-policy output SHAPE_WAN
07-09-2019 08:28 PM
Hi,
You use the "mls qos trust dscp" to classify the traffic. (based on the DSCP)
For output, you need to configure the "queue". Look this:
https://community.cisco.com/t5/telepresence-and-video/help-understanding-qos-threshold/td-p/1374101
P.S. depending on the model of the switch the command changes due to queues and threshold, for example, on slide 47 shows that the 2960 switch queue is 1P3Q3T (1 priority, 3 queue, 3 threshold)
https://www.ciscolive.com/c/dam/r/ciscolive/emea/docs/2019/pdf/BRKCRS-2501.pdf
07-10-2019 09:34 AM
07-10-2019 03:36 PM
Hello
Can you elaborate further on your topology regards these two sites, explain how are they connected together, what type of connection is being used on the wan interface ( l2/l3 p2p, vpls.etc..), are you suing any routers, dynamic routing ?
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