Re: Cat6500 oversubscription

The worst thing is that Cisco 6500 has lower throughput than other vendors.
by using sup720 -720Gb and with VSS max is 1.4T
For 6509 switches -40G (Full-duplex) for each slot using sup720 (If VSS it
will be 80)
For 6513 Switches -20G (1-8 slots) and 40G (9-13 slots) with sup720

If you are using 48 port 10/100/1000 module in 6509 (2 x 20 gbps fabric
channel to sup720 cross bar switch fabric).
To avoide oversuscribtion you should have 1:1 in datacenter side where as
4;1 (distribution to Core is preferable)

Thanks
Shahid Ansari
CCIE#20017

On Fri, Sep 17, 2010 at 5:27 PM, Peter Kurdziel <usaccie_at_gmail.com> wrote:

> Hi Antonio,
>
>
>
> I ran into this earlier this year. You should see drops on all the ports
> within an asic. Eight ports at a time will show drops. You'll notice a
> pattern with the ports that are dropping traffic vs the ports that are not.
>
> Try something like sh int | in drops to quickly identify a pattern and
> check
> all the ports for a few days.
>
> The switching module has 48 oversubscribed ports in six groups of eight
> ports each:
>
> -
>
> Ports 1, 2, 3, 4, 5, 6, 7, 8
> -
>
> Ports 9, 10, 11, 12, 13, 14, 15, 16
> -
>
> Ports 17, 18, 19, 20, 21, 22, 23, 24
> -
>
> Ports 25, 26, 27, 28, 29, 30, 31, 32
> -
>
> Ports 33, 34, 35, 36, 37, 38, 39, 40
> -
>
> Ports 41, 42, 43, 44, 45, 46, 47, 48
>
> The eight ports within each group use common circuitry that effectively
> multiplexes the group into a single, nonblocking, full-duplex Gigabit
> Ethernet connection to the internal switch fabric. For each group of eight
> ports, the frames that are received are buffered and sent to the common
> Gigabit Ethernet link to the internal switch fabric. If the amount of data
> received for a port begins to exceed buffer capacity, flow control sends
> pause frames to the remote port to temporarily stop traffic and prevent
> frame loss.
>
> If the frames received on any group exceeds the bandwidth of 1 Gbps, the
> device starts to drop the frames. These drops are not obvious as they are
> dropped at the internal ASIC rather than the actual interfaces. This can
> lead to slow throughput of packets across the device
>
> If more throughput is required, either use ports from a line module that
> does not use oversubscription, or use ports from different port-groupings
> on
> oversubscribed line modules. For example, if the line module has 48 ports
> in
> groups of eight, you can select ports 1, 9, 17, 25, 33, and 41 for the same
> port channel.
> HTH
>
> --
> Regards,
> Peter Kurdziel
> CCIE# 25418
>
>
>
> On Fri, Sep 17, 2010 at 7:00 AM, Antonio Saez <
> antonio.saez.jimenez_at_gmail.com> wrote:
>
> > Hi all,
> >
> > I am trying to indentify if there are loss of frames due oversubscription
> > in
> > a 6500 with ws-x6548-ge-tx linecards. I have found some documents talking
> > about "overruns" counter, some other talking about "qos3Outlost" counter.
> >
> > what is the right counter I have to check?
> >
> >
> > Regards
> >
> >
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Received on Fri Sep 17 2010 - 19:08:47 ART