Re: 3750 switch hardware buffer :(

Actually, Dale, that's partly true.

1. 2960/3560/3750 do have a very similar hardware architecture, with
internal rings running between asics. When there is only one ASIC, the
packet moves from ingress ring to egress ring via an internal loopback
interface.

2. There is a difference in types of switches, primarily 8/12/24/48 port and
Gig/Non-Gig.

3. There is a rule of thumb you can use: 10/100 switches have always 2MB
shared SRAM buffer for egress, therefore 24-port or 48 port all have the
same buffer size. This space is shared among all the ports, but can be
reserved.
A very descriptive but not too accurate guide is written by Cisco on buffer
segmentation and reservation is here:
http://www.cisco.com/en/US/products/hw/switches/ps5023/products_tech_note09186a0080883f9e.shtml

4. For Gigabit switches, there are different ASICS, and to understand what
you're doing you have to first map a port to ASIC.
All ports that fall under one ASIC share one buffer - it's the 384KB and is
located directly on the ASIC. So for example port 1 (connected to ASI3) is
never be able to use buffers of port 2(connected to ASIC 0). Ports are not
connected to ASICs sequentially. e.g. to ASIC 3 you'll have the following
ports connected: 1,5,8,13, etc...

This is for egrees buffers.

On Mon, May 18, 2009 at 12:52 PM, Dale Shaw <dale.shaw_at_gmail.com> wrote:

> Hi,
>
> On Mon, May 18, 2009 at 8:41 PM, dave dave <funccie_at_gmail.com> wrote:
> >
> > I wanted to kneo 3750 hardware buffer, I am unable to find it on Cisco as
> > well as on the box itself. Can you please point me to some URL or tell me
> > the command to check the hardware of 3750.
>
> This was asked on cisco-nsp today --
>
> https://puck.nether.net/pipermail/cisco-nsp/2009-May/060703.html
>
> John Jensen jensenja at gmail.com
> Mon May 18 04:52:20 EDT 2009
>
> "0.75MB of ingress buffering is dynamically divided into port
> buffers/queues, 2 of which are user-configurable. There's 2MB of
> egress buffering that provides 4 egress queues per physical port."
>
> Does that help?
>
> cheers,
> Dale
>
>
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