[c-nsp] Egress QoS on FE links with less than 100Mbps speeds

[Lobo]

Wow thanks Daniel that did the trick on the 3750 platform!  Here's a 
sample config in case anyone ever needs it:

interface FastEthernet1/0/23
  switchport trunk encapsulation dot1q
  switchport trunk allowed vlan 666-670
  switchport mode trunk
  load-interval 30
  srr-queue bandwidth share 1 25 35 40
  srr-queue bandwidth shape  10  0  0  0
  srr-queue bandwidth limit 80
  priority-queue out
  mls qos trust dscp
  spanning-tree portfast

Jose


On 12/16/2009 10:04 AM, Bielawa, Daniel W. (NS) wrote:
> Hello,
> 	We had the same issue on couple of links. We solved it with the following command. The number on the end is a percentage of link speed in 1 percent increments. This was done on a 3750G running 12.2(44)SE6, this command might or might not work on other platforms.
>
>   srr-queue bandwidth limit (10-90)
>
> Thank You
>
> Daniel Bielawa
> Network Engineer
> Liberty University Network Services
> Email: dwbielawa at liberty.edu
> Phone: 434-592-7987
>
>
> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Lobo
> Sent: Wednesday, December 16, 2009 8:45 AM
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] Egress QoS on FE links with less than 100Mbps speeds
>
> We're doing some Catalyst testing to roll out QoS on our Ethernet
> network and have come up against a hurdle.  On most of our backbone
> links in a MAN, the actual bandwidth between one C/O to another C/O is
> not always 100Mbps.  There are times when the link is only capable of
> hitting say 80Mbps (we're a wireless isp) or less.
>
> Since we have to use a FE port for this type of connection, do the
> switches believe that they have 100Mbps of bandwidth to play with when
> putting packets into the appropriate queues?
>
> I'm a bit confused as to how the switches work in this fashion.  If I
> were using CAT5 cables or fiber this would be simple to understand as
> the bandwidth would be fixed.  :)
>
> This is an example of a configuration on a 3550-24 that I'm using:
>
>
> interface FastEthernet0/x
> mls qos trust dscp
> wrr-queue bandwidth 40 35 25 1
> wrr-queue cos-map 1 0 1
> wrr-queue cos-map 2 2
> wrr-queue cos-map 3 3 4 6 7
> wrr-queue cos-map 4 5
> priority-queue out
> !
>
> The switches that we use are 2950, 3550, 3750 and 6524s.
>
> With MQC and "layer 3" QoS, I would know how to fix this by simply using
> the "bandwidth" command on the physical interface and basing my output
> policy-map to use "bandwidth percent" for each class.  Layer 2 QoS
> doesn't seem to work this way though.
>
> Any help would be appreciated.
>
> Thanks.
>
> Jose
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