[c-nsp] Cisco 650x sup2 / sup32 configuration - what makes sense?

John Gill johgill at cisco.com
Wed Dec 7 18:09:53 EST 2011

Hi Jeff,
The issue is more likely the port asic buffering here.  Just a hunch, 
but do you have any 10Mb ports connected close to your 1Gb interfaces on 
the 6148-GE-TX?

Ports share buffers in blocks of 8: 1-8, 9-16, etc...

If you have a 10Mb or 100Mb port in line with a 1Gb interface, you can 
have contention for buffers easily.  There are some commands we can use 
to check this:
show counters interface gigabitEthernet x/y | include qos3Outlost

remote login switch
show platform hardware asicreg pinnacle slot x port y err (cleared on read)

You could also do some slightly intrusive debugging where we reduce the 
port buffers but are able to see which ports are truly oversubscribed 
and affecting the others:
Here are the commands needed to disable head of line blocking on this
type of card:
6500(config)#service internal
6500(config)#interface gigabit 1/1
6500(config-if)#hol-blocking disable
%HOL Blocking is Disabled on: Gi1/1 Gi1/2 Gi1/3 Gi1/4 Gi1/5 Gi1/6 Gi1/7

Verify hol-blocking is disabled:
6500#show hol-blocking module 1

Interface         Hol-Blocking
-------------- ---------------
Gi1/1             Disable
Gi1/2             Disable
Gi1/3             Disable
Gi1/4             Disable
Gi1/5             Disable
Gi1/6             Disable
Gi1/7             Disable
Gi1/8             Disable

Once this is disabled, the drops will move to the interface counters and 
can be seen with 'show interface gigabit <mod/port>'.  Since it is
recommended to keep hol-blocking enabled, this information can be used
to find the device that is overrunning the buffers on the range of port
and move it to another card or an isolated range on the card so
hol-blocking can be re-enabled.

John Gill

On 12/7/11 5:10 PM, Jeff Meyers wrote:
> Hello list,
> I am looking for a configuration, that makes sense. A 6509 is currently
> equipped with a sup2, some 6516-GBIC modules and some 6148-GE-TX
> modules. The sup2 will be replaced with a sup32-10GE soon but we're
> having trouble with the interfaces modules as well.
> When a customer bursts a GigE port on the 6148-GE-TX, the available
> bandwidth on all other ports (at least ports 1-24 which seem to share an
> asic) are affected as well although there is not more than just
> 2-3GBit/s of traffic on the whole module. What is the best choice here
> to have reasonable amounts of bandwidth available across the whole box?
> The upcoming redundant sup32 will use a few GBit/s and the rest will be
> required on the GBic and TX module. Both modules shall be capable of
> consuming something around 8GBit/s+ in total without causing trouble on
> the direct neighbour ports when bursting.
> Does it make sense to replace the 6148-GE-TX with a 6748 or is the sup2
> respectively the sup32 the actual bottleneck?
> Is there a way to find out the available bandwidth for each module in
> the running configuration?
> Thanks & best regards,
> Jeff
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