[c-nsp] Nexus 5K optimisation for iSCSI traffic

[Brad Hedlund (brhedlun)]

No. The FEX has BPDU Guard logic running in hardware. The moment a BPDU is received on the port it will be disabled.

On the blade switches you can implement:
1) Flex Links (safe)
2) Egress BPDU filter (risky)
3) Disable STP (dangerous)

For #2 and #3, a misconfigured or missing LACP config can cause a loop.
For #3, a misconfigured server NIC teaming can cause a loop. 

Cheers,
Brad
http://bradhedlund.com 

Sent from my iPad
(please excuse brevity, typos)

On Aug 5, 2011, at 9:49 AM, "Matthew Melbourne" <matt at melbourne.org.uk> wrote:

> Can P prevent a FEX port being disabled by implementing bpdufilter, or
> do we need to ensure that BPDUs aren't receiving on FEX ports?
> 
> We were hoping to use LACP between the downstream switch and the FEXes
> as a poor-man's loop prevention mechanism.
> 
> Cheers,
> 
> Matt
> 
> On 5 August 2011 15:17, John Gill <johgill at cisco.com> wrote:
>> It would be filter toward the FEX ports on your blade switches, but not on
>> the FEX ports themselves. Whether you turn STP off or not on the blades, the
>> FEX doesn't know. Just remembering if you create a loop, you no longer have
>> the protection of STP; you are intentionally tricking the FEX into not
>> knowing there is a switch downstream.
>> 
>> Regards,
>> John Gill
>> cisco
>> 
>> On 8/5/11 9:59 AM, Matthew Melbourne wrote:
>>> 
>>> Thanks for that - that's another issue we've encountered. I am hoping
>>> we can implement bpdufilter on the FEX ports (as well as disabling STP
>>> on downstream switches).
>>> 
>>> On 5 August 2011 14:12, Brad Hedlund (brhedlun)<brhedlun at cisco.com>
>>>  wrote:
>>>> 
>>>> Note that the FEX will disable any port that receives a BPDU, by design
>>>> in hardware.  You will need to disable STP on the blade-switch-to-FEX links
>>>> for this to work. If it's Cisco blade switches you can use Flex Links.
>>>> 
>>>> Cheers,
>>>> Brad
>>>> http://bradhedlund.com
>>>> 
>>>> Sent from my iPad
>>>> (please excuse brevity, typos)
>>>> 
>>>> On Aug 5, 2011, at 6:08 AM, "Matthew Melbourne"<matt at melbourne.org.uk>
>>>>  wrote:
>>>> 
>>>>> Hi,
>>>>> 
>>>>> We're implementing two pairs of N5Ks (and downstream N2k FEXes) to act
>>>>> as separate iSCSI SAN fabrics, with SAN heads attached directly to
>>>>> N5Ks and host ports (and downstream integrated blade switches)
>>>>> connecting to the FEXes. Does anyone have any real-world experience of
>>>>> using N5Ks for a large iSCSI deployment. I have enabled jumbo frames
>>>>> through a network-qos policy-map as an obvious first-step, but wonder
>>>>> whether anything can be optimised by tuning buffer sizes to
>>>>> accommodate the bursty nature of iSCSI (etc)? This switches will only
>>>>> be switching iSCSI traffic.
>>>>> 
>>>>> Cheers,
>>>>> 
>>>>> Matt
>>>>> 
>>>>> --
>>>>> Matthew Melbourne
>>>>> _______________________________________________
>>>>> cisco-nsp mailing list  cisco-nsp at puck.nether.net
>>>>> https://puck.nether.net/mailman/listinfo/cisco-nsp
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>> 
> 
> 
> 
> -- 
> Matthew Melbourne