[c-nsp] Fabricpath on Nexus

[Lincoln Dale]

On 29/03/2011, at 6:41 AM, Asbjorn Hojmark - Lists wrote:

>> We are considering deploying a pair of Nexus 7010 switches using
>> fabricpath for L2 and HSRP for Layer 3.
> 
> If it really is only two boxes, FabricPath provides *no* benefits,
> only more complexity

strongly disagree.
more than happy to have a clueful discussion.

1. FabricPath adds no complexity compared to traditional L2 (STP).

If anything, its actually simpler as there are less nerd knobs for one to tune for "best practice" behavior, since its 'new' technology many of the best practice things are just default behaviour.


2. Benefits

 - you can evolve your network to far more ports active from any path to any other path active/active

 - you get a lot more flexibility in the topology you build.  no need to build in a hierarchy or tree.  or you can if you wish.  or make it partially ringed.  or not.  the system doesn't care and all paths are still used active.

 - FabricPath has significant convergence advantages over STP
   (see http://www.networkworld.com/community/blog/ciscos-fabricpath-makes-grade)

 - "conversational MAC learning" is enabled by default.  this means that unlike traditional L2 networks
   where all switches end up with a synchronised view of the MAC table, in FabricPath not only don't
   the 'core' switches don't have to know edge devices' MAC addresses but individual edge ports only
   learn MAC addresses where there is bidirectional communication going on.
   net-net: this means that far larger L2 networks can be built with far smaller MAC tables.

there are countless other benefits too, full backwards computability with traditional ethernet & spanning tree, so none of it is a rip-and-replace but rather an evolutionary thing.
there are also benefits in terms of how one can enable active/active towards traditional classical ethernet bridges & STP -- and how one can scale the number of anycast / active/active gateways into L3.

there are other benefits too, but thats the high level.


cheers,

lincoln.