10-25-2015 03:46 PM - edited 03-05-2019 02:35 AM
Hi All, we are implementing our new Shortel phone systems requires us to match IP DSCP EF, Protocol RTP Audio, IP DSCP AF31.
It requires us to reserve 20% of bandwidth in its highest priority queue and 20% of signaling in the medium queue.
Below is what I had mapped out but, It looks like the 3750 switches will not apply to the output side of the interface.
class-map match-any Audio
match ip dscp ef
match protocol rtp audio
class-map match-any Control
match ip dscp af31
!
policy-map voice
class Audio
priority percent 20
set ip dscp ef
class Control
bandwidth 20
set ip dscp af31
class class-default
set dscp default
fair-queue
The error I get is "Warning: Assigning a policy map to the output side of an interface not supported"
How can I accomplish the above when I cannot apply to the output side of my routed nterface?
Thanks,
Daniel
10-26-2015 12:27 AM
Hello Daniel
On these Catalyst switches you only have limited options for configuring QoS when compared to a router. The non-metro version of 3750 (and the 3750-X) doesn't support outbound CBWFQ / LLQ using MQC syntax. You are limited to 4 egress queues, one of which can be configured as a priority queue and then you can apply shaping to adjust the outgoing traffic rate. Remember, that using MQC you can police/mark your traffic (DSCP) in the inbound direction on an interface. Maybe you could split your service-policy into two sections and apply marking inbound and then queuing/scheduling outbound.
You might want to have a look at the configuration guide here http://www.cisco.com/c/en/us/support/docs/switches/catalyst-3750-series-switches/91862-cat3750-qos-config.html#qds and also at this post: https://supportforums.cisco.com/discussion/11238706/srr-queue-and-traffic-prioritization#3397944
Best regards,
Martin
10-26-2015 05:21 AM
Disclaimer
The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.
Liability Disclaimer
In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.
Posting
Ditto to what Martin has noted.
In addition, on a 3750, you need to enable QoS globally to take advantage of its QoS features, and when you do, by default, ingress traffic that is already marked will have its markings erased. Also the 3750's default QoS settings often increase egress drop rates without some buffer setting tuning.
Also unlike CBWFQ, there's no default class nor FQ equivalent. You need to insure traffic goes to the egress queue (one of four) you desire. Each hardware egress queue only supports FIFO although with one of three tail drop settings.
Martin mentioned shaping. A 3750 can shape a queue or the port. If your egress has some logical bandwidth limit, less that port speed, you normally want to shape the port, but also be aware the port shaper is a bit inexact, so you might need to shape slower than your really want to avoid exceeding downstream bandwidth caps.
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide