[c-nsp] Redundant switch fabric

[Tony Varriale]

I've had a colleague run into an issue going to 4.1.3 (long story but it's 
intrusive either way you slice it and is how all boxes are).  What was your 
upgrade from and to?

tv
----- Original Message ----- 
From: "Justin C. Darby" <jcdarby at usgs.gov>
To: "Brad Hedlund" <brhedlun at cisco.com>
Cc: <cisco-nsp at puck.nether.net>
Sent: Tuesday, March 31, 2009 11:51 AM
Subject: Re: [c-nsp] Redundant switch fabric


> Mike,
>
> Just to chime in here a bit with some experience - we've had Nexus 7K 
> switch backplane modules fail - unless you are pushing near 100% backplane 
> utilization you don't even notice until it emails you or your config 
> monitoring program notices the failed module. In recent NX-OS releases, In 
> Service Software Upgrades are working properly 100% of the time for us, 
> and outside of the fact it can take 3-4 hours to upgrade a fully loaded 
> switch, there's no real downtime if you've got working port redundancy 
> across modules, and modules only go down one at a time like they're 
> supposed to.
>
> Considering how distributed and redundant components of the switch are - 
> it's pretty unlikely you'd run into huge redundancy problems with any 
> single component. I don't have enough N7K's to play with Virtual Port 
> Channels (vPCs), but it'd be interesting to see if they have any issues 
> when upgrading switches. vPCs can add extreme (and usable) redundancy to 
> multi-chassis design, if you want to go a step farther.
>
> Justin
>
> P.S. Comments made here are my own and should not in any way be considered 
> an endorsement by the U.S. Federal Government.
>
> Brad Hedlund wrote:
>> Mike,
>> The 6500 and 4500 have the "switch fabric" on the supervisor engines, so 
>> by
>> having dual supervisors, you in effect have a redundant fabric.
>>
>> The 6748 actually has 4 traces, each 20G.  2 traces connect to the active
>> supervisor containing the active switch fabric.  The remaining 2 traces 
>> are
>> standby connections to the standby supervisor/fabric.  So, when a 
>> supervisor
>> engine and its fabric fails, the 2 standby traces are enabled and the 
>> full
>> 40G of bandwidth remains.  You never, under normal circumstances, have 
>> only
>> a single trace active on 6748.  Newer versions of IOS provide a "hot
>> standby" fabric feature which allows this fabric trace switch over to 
>> happen
>> faster - roughly 50ms.
>>
>> For the best in redundant designs, consider the Nexus 7000, where the 
>> switch
>> fabric is decoupled from the supervisor engines into a series redundant
>> "fabric modules" installed into the back of the switch.  Should a 
>> supervisor
>> engine fail in Nexus 7000 there is ZERO impact to the switch fabric, 
>> because
>> the supervisor engine does not forward data plane traffic.
>>
>> Cheers,
>>
>> Brad Hedlund
>> bhedlund at cisco.com
>> http://www.internetworkexpert.org
>>
>>
>> On 3/31/09 9:05 AM, "Mike Louis" <MLouis at nwnit.com> wrote:
>>
>>
>>> I have a solution design that requires redundant switch fabrics. I am
>>> interpreting this beyond just have redundant supervisors meaning 
>>> redundant
>>> backplanes on the switch cards. Do the 6500 and 4500 support redundant
>>> fabrics? Will a 6748 function with one trace failed?
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