[c-nsp] Redundant switch fabric

[Brad Hedlund]

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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