Re: 3560: Queuing and WRD at less than interface rate posted 09/26/2008
- Subject: Re: 3560: Queuing and WRD at less than interface rate
- From: "Petr Lapukhov" <petr@xxxxxxxxxxxxxxxxxxxxxx>
- Date: Fri, 26 Sep 2008 18:52:32 +0400
- Cc: "Cisco certification" <ccielab@xxxxxxxxxxxxxx>
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On the 3560 platfor, you can use the command "srr-queue bandwidth limit" to
enforce interface-wide shaping (it actually is shaping, since it delays
packets). Combined with speed manipulation (10/100/1000) you can "shape"
interface to as little as 1Mbps (with some granularity for speed values, of
At the same time, you can configure the use of SRR queues (either in shaped
or shared modes) with this feature. In effect, this allows implementing
hierarchical shaping, with per-interface shaped rate combined with per-queue
Of course, there are just four-queues and therefore four aggregate traffic
classes. But this is the price you have to pay for the high switching
Petr Lapukhov, CCIE #16379 (R&S/Security/SP/Voice)
Internetwork Expert, Inc.
Toll Free: 877-224-8987
Outside US: 775-826-4344
2008/9/26, Brian Landers <brian@xxxxxxxxxxxxxx>:
> Hi all,
> I have two 3560's connected by Metro Ethernet. The MetroE is policed to
> 10mb by the service provider, but delivered as 100/full on copper. Thus,
> far as my switches know, they're connected by a 100mb link.
> Here's the tricky part: I need to do some fun QoS stuff like priority
> queuing, WRD, and class-based fair-queuing across this link, based on the
> 10mb CIR. Currently, since the hardware queues never fill up, the queuing
> and WRD never kick in. Is there a way to force the 3560 to use a different
> value for its "start queueing now" water mark?
> Yes, this is technically off-topic for the CCIE list, but it seems like
> is just the kind of scenario someone evil like Scott would come up with for
> a question: "R1 and R2 are connected by 100mb ethernet. Pretend it's only
> 10mb and implement WRD"
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