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Beginner

First QoS Deployment

We have maintained a data network for a company that cosists of 8 WS-C2960-24TC-S and WS-C2960-48TC-S switches, and a CISCO1921/K9router.  Our client's phone vendor has chosen to implement Allworx IP phones.  They are requring the following topology: Catalyst Sw > Allworx IP Phone > Workstation.  switchport voice vlan x and spanning-tree portfast have been configured on the connecting interfaces.  The Allworx phones are being successfully placed in the voice VLAN via CDP.

The phone vendor has come back to me with two major issues:

1.  The phones have an echo.

2.  After a few minutes of being restarted, the phones' buttons start blinking erratically.

The phone vendor requested I deploy broadcast/multicast storm control.  I have applied storm-control broadcast level x and storm-control-multicast level x on all interfaces with no difference.   show storm-control revels 0% usage.  After telling the phone vendor this, they want me to deploy QoS on all access switches.  As I have never done this before, I am currently researching on how to do this.

My goals are to give all traffic on the voice vlan / voice traffic higher precedence/priority to avoid delay, jitter, echo, etc.  Also, I do not have access to their equipment.

Is there an example configuration I can refer to, or some pointers, so I can implement my goals listed above?  I am planning on studying for CCNP Switch soon, but unfortunately need this deployed immediately.

Thank you

8 REPLIES 8

First QoS Deployment

Hi John,

You can try applying an inbound service policy to these switch ports using MQC (Modular QoS CLI)

For example, assuming the following details about IP Phone

IP Phone Subnet:  192.168.0.0/24

First configure an extended ACL to match traffic originated from IP Phone

access-list 101 permit ip 192.168.0.0 0.0.0.255 any

Next, create a class-map and call the ACL  under this as a match criteria,

class-map IP_PHONE

match access-group 101

Then create a Policy map and call the class-map "IP_PHONE" under this and assign DSCP value as CS5

policy-map IP_PHONE

class IP_PHONE

set dscp cs5

Finally apply this policy-map to the switch ports.

int fa0/1

service-policy input IP_PHONE

This will ensure that all traffic from IP phones are marked with CS5 which by default will be handled as high priority traffic in switch Queues.

Rajmohan R

Rajmohan R
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Beginner

First QoS Deployment

Unfortunately, I am running C2960-LANLITEK9-M software so I have neither the class-map or policy-map commands.

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VIP Expert

Re: First QoS Deployment

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

It's often unusual to need QoS enabled on LAN switches, and on the 2960 series, enabling QoS can easily reduce performance because of default buffer sharing.  However, as you are sharing the same port for both the VoIP phone and the workstation, port QoS might be needed to keep a busy workstation from being adverse to the VoIP phone.

I'm concerned with your 1921.  Cisco only recommends the 1921 for up to 15 Mbps of WAN bandwidth (although this is a conservative rating).  It's easy to overload a small ISR used for LAN routing.  It's also easy to congest on low bandwidth WAN links.

BTW, I have seen issues where some VoIP phones don't deal well with busy workstations that transit through them.

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Beginner

First QoS Deployment

Ok.  At this point let me re-phrase my question.  How can I accomplish what Rajmohan is suggesting with the C2960-LANLITEK9-M image?

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VIP Expert

First QoS Deployment

What version of IOS?

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Beginner

First QoS Deployment

12.2(55)SE5

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Beginner

First QoS Deployment

Update:

I mapped the phone's CoS value (7) to ingress queue #2

mls qos srr-queue input cos-map queue 2 7

And gave the queue 10% bandwidth

mls qos srr-queue input priority-queue 2 bandwidth 10

I am a little confused on the threshold values.  If queue 1 uses 100% of it's queue (90 Mbps), will it drop packets to reserve the 10% priority set in queue 2, or do I need to configured threshold values (WTD) to get this functionality?

SW1#show mls qos maps cos-input-q

   Cos-inputq-threshold map:

              cos:  0   1   2   3   4   5   6   7

              ------------------------------------

  queue-threshold: 1-1 1-1 1-1 1-1 1-1 2-1 1-1 2-1

SW1#show mls qos input-queue

Queue     :       1       2

----------------------------------------------

buffers   :      90      10

bandwidth :       4       4

priority  :       0      10

threshold1:     100     100

threshold2:     100     100

Thank you

Highlighted
VIP Expert

Re: First QoS Deployment

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

That ingress queue is for fabric access, you shouldn't need to change that.

LAN-Lite says it supports QoS, but from the documentation I briefly reviewed, limitations aren't well defined.

If you cannot use "typical" port ingress QoS, perhaps you can use VLAN based QoS and just tagged all your VoIP traffic as desired.  VoIP phones usually can tag their traffic, and if they do, you would need to concern yourself with different traffic treatment based on ToS markings.  Again, this can be somewhat tricky on a low end switch and often isn't needed on such switches.

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